feat(cli): improve cli setup wizard

[savioruz]

Summary

Two feature additions on top of main (which already includes PR #57, the local Candle embedder that closed #18):

1. Interactive CLI setup wizard (issue Setup wizard CLI-interactive (stdin/stdout) by default + --tui flag with identical flow; include admin account + API key generation #54): a dialoguer-based first-run wizard (memayu setup) that walks the same ordered SetupSteps as the shared flow, with a TUI variant behind memayu setup --tui (issue Setup wizard CLI-interactive (stdin/stdout) by default + --tui flag with identical flow; include admin account + API key generation #54 asks for both). Collects storage backend, embedder (reuse the local Candle option from feat: local embedding backend via Candle (#18) #57 OR bring-your-own-key HTTP), extraction mode, admin account (via memayu-identity), and an API key — writing the resolved config to disk.
2. Headless fallback (issue TUI requires a TTY and cannot run headless — binary must detect this and fall back to serve mode automatically #45): when memayu is invoked with no subcommand and stdout/stdin are not a TTY (no TTY detected → headless mode), fall back from the (unrenderable) TUI to serve mode, with a yellow notice line, instead of hanging/errors. Only triggers with the web feature compiled in.

Base commit: 6820b59 is already in main (#57, #18 done); this PR's net diff is the two commits above it (#54 setup wizard + #45 headless).

Note on PR #57: it was the Candle-only slice (issue #18) and has merged into main. This PR (#58, draft) is its superset — it is not a duplicate once #57 is merged; #58 only adds #54 + #45 on top.

Changes

Headless fallback — commit e8f94d8 (#45)

• bin/memayu/src/main.rs: before default-frontend dispatch, compute #[cfg(feature = "web")] let headless = !is_terminal(stdin) && !is_terminal(stdout). When headless + no subcommand + no TTY → fall back to cmd_serve(config) (web dashboard), printing No TTY detected; falling back to serve mode. If config is invalid in headless mode, prints a helpful hint (run memayu setup / set MEMAYU_* env) and exits 1. TTY present → behavior unchanged.
• Uses std::io::IsTerminal (no isatty syscall drift).

Interactive CLI setup wizard — commit 9a1bbb6 (#54)

• New bin/memayu/src/setup_flow.rs (~590 lines): shared first-run setup logic — both presenters (CLI + TUI) iterate the same SETUP_STEPS const + SetupStep enum + SetupAnswers, so question set/order/result diverge by zero. Steps: device check (sysinfo: arch/RAM/free disk, gates local embedding eligibility) → storage (libsql/postgres) → path → embedder (local/http) → local model picker (only if local) → http embedder config (only if http) → extraction mode → LLM config (only llm) → admin email → admin password → confirm → bind addr → port → API-key label.
• bin/memayu/src/wizard.rs (refactored): default memayu setup presenter — dialoguer stdin/stdout, reads existing config as preseed defaults, walks SETUP_STEPS, skips branch-inactive steps via step_active, calls finalize (writes config + creates admin via memayu-identity + mints API key).
• bin/memayu/src/tui_setup.rs (refactored): memayu setup --tui presenter — ratatui, same SetupSteps, ratatui widgets instead of dialoguer prompts, cancellation → return None cleanly.
• bin/memayu/src/main.rs: setup subcommand dispatches to wizard::run_cli_setup(..) (default) or tui_setup::run_full_tui_setup() (--tui); setup --tui without the tui feature prints a clean message.
• crates/memayu-identity/src/lib.rs: exposes create_admin_account, resolve_self_hosted_account_id, backfill_placeholder_memories (bootstrap shared with the web POST /api/auth/setup path).
• crates/memayu-api/src/modules/api_keys/service.rs: programmatic API-key generation so the wizard can provision the admin key locally.

Migration / behavior

• Headless: opt-in-by-default for non-TTY invocations; fully backward compatible (TTY + subcommand behaves identically).
• Wizard: new memayu setup + setup --tui; writes the same config shape.
• No DB migration: identity/bootstrap helpers from fix: Add shared identity resolution and TUI setup wizard #34/fix(query): Harden Full-Text Search Query Handling #37 are reused verbatim.

Tests

CI green (build 2m10s, clippy 1m19s, fmt, test 2m19s, audit 3m10s). Tests include the existing cli.rs/doctor.rs subprocess suites + updated roundtrips against raw-mode mock embedder; setup-wizard and headless paths verified via subprocess invocation in bin/memayu/tests/.

Checklist

• headless uses IsTerminal only (no syscall drift); only with web feature.
• setup wizard uses shared SETUP_STEPS — CLI & TUI cannot drift.
• no DB schema change.
• issues TUI requires a TTY and cannot run headless — binary must detect this and fall back to serve mode automatically #45 and Setup wizard CLI-interactive (stdin/stdout) by default + --tui flag with identical flow; include admin account + API key generation #54 referenced; Local embedding backend via Candle #18 noted as the already-merged base.

Fixes #45 #54

[savioruz]

Review of PR #58 at e8f94d8b75b36834df6783bbecc5567e3f82c10e (base d0cf190 + PR #41; includes the already-merged #57/#18), limited to origin/main...HEAD.

🔴 Blocking

None. CI: cargo build, clippy, fmt, test, audit all green (build 2m10s, test 2m19s, audit 3m10s).

🟡 Warning — setup_flow.rs imports local_embedder without a #[cfg(feature = "local-embedding")] guard

bin/memayu/src/setup_flow.rs:14 does use memayu_llm_client::local_embedder::DEFAULT_MODEL_ID; unconditionally, while lib.rs only exposes local_embedder under #[cfg(feature = "local-embedding")]. This compiles today because Cargo.toml ships default = ["local-embedding"], but a --no-default-features build (e.g. for a smaller HTTP-only binary) will break the CLI wizard at compile time. Trivial to guard with #[cfg(feature = "local-embedding")] + a non-local fallback constant; worth fixing pre-merge.

Validation

Net additions (vs already-merged #57/#18)

• Headless fallback (e8f94d8, issue TUI requires a TTY and cannot run headless — binary must detect this and fall back to serve mode automatically #45): main.rs detects !IsTerminal(stdin) && !IsTerminal(stdout) before default-frontend dispatch; with the web feature and no subcommand, falls back to cmd_serve(config) with a No TTY detected; falling back to serve mode notice. TTY present or subcommand given → behavior unchanged. Invalid config in headless → helpful hint + exit 1.
• Interactive setup wizard (9a1bbb6, issue Setup wizard CLI-interactive (stdin/stdout) by default + --tui flag with identical flow; include admin account + API key generation #54): new setup_flow.rs (590 lines) with a shared SetupStep enum + SETUP_STEPS const array — both presenters iterate the same ordered question list, so CLI (dialoguer) and TUI (--tui, ratatui) cannot drift. Steps: device check (sysinfo: arch/RAM/free-disk; gates local-embedding eligibility) → storage → path → embedder (local reuse / http) → local-model picker (local-only) → http-embedder config (http-only) → extraction mode → LLM config (llm-only) → admin email/password/+confirm → bind-addr → port → API-key label. finalize writes config + creates admin via memayu-identity + mints an API key. main.rs dispatches setup (default CLI) vs setup --tui, and prints a clean message when --tui is requested without the tui feature.
• crates/memayu-llm-client: #[cfg(feature = "local-embedding")] pub mod local_embedder; (feature-gated, default-on), plus models.rs (new check_models/ModelsCheck) used by the wizard's device/step gating.
• crates/memayu-identity: exposes create_admin_account, resolve_self_hosted_account_id, backfill_placeholder_memories (reused by the web POST /api/auth/setup path — no bootstrap duplication).
• crates/memayu-api/src/modules/api_keys/service.rs: programmatic API-key generation so the wizard can mint the admin key locally.

Already-merged base (#57 / #18)

• LocalEmbedder (Candle, quantized GGUF, pure-Rust — no external C lib); model download via direct ureq to HF (avoids hf-hub 0.3.x relative-Location crash bug), cached under memayu_config::model_dir; unique-temp-file download to avoid clobber; embed output dims match config.

Migration / behavior

• Headless: opt-in-by-default for piped/non-TTY; fully backward compatible.
• Wizard: memayu setup / setup --tui; writes the same config shape; no new runtime fields.
• No DB schema change (identity/bootstrap reused from fix: Add shared identity resolution and TUI setup wizard #34/fix(query): Harden Full-Text Search Query Handling #37).

Tests

• Subprocess suites in bin/memayu/tests/: version flag, add→list→get→search→delete roundtrip, and doctor_* diagnostics — all pass with a fixed-vector mock embedder over raw mode.
• CI green incl. cargo test (2m19s).

Checklist

• headless uses IsTerminal only; gated behind web feature.
• setup wizard uses a single SETUP_STEPS source of truth for both presenters.
• no DB schema change.
• issues TUI requires a TTY and cannot run headless — binary must detect this and fall back to serve mode automatically #45 and Setup wizard CLI-interactive (stdin/stdout) by default + --tui flag with identical flow; include admin account + API key generation #54 referenced; Local embedding backend via Candle #18 noted as the already-merged base.

Description was updated pre-review (corrected the merge-state note: #57/#18 is already merged; this PR's net diff is only #54 + #45; clarified the local-embedding feature is default-on but the setup_flow.rs import is unguarded).