feat(builtins): make, a GNU make subset run in the sandbox shell

Driver-based make: parses makefiles (assignments, conditionals, define,
include, explicit/pattern/static/suffix rules, target-specific vars,
special targets), expands functions incl. $(shell)/$(wildcard), and runs
recipes as sh -c in the interpreter. New PlanStep::Capture/Emit keep
$(shell) output captured and make's messages ordered with recipe output.
Gaps L-MAKE-001..003, caps TM-DOS-126.

Claude-Session: https://claude.ai/code/session_019aFikmptPc91Fj4N2iDXQA

Author: chaliy

crates/bashkit/docs/compatibility.md

@@ -99,6 +99,7 @@ for sandbox security reasons. See the compliance spec for details.
 | `disown`, `fg`, `bg` | `[JOBSPEC]` | `fg` waits; `bg` is a no-op (jobs already run) |
 | `uuidgen` | `-r` | Random (v4) UUID from the OS CSPRNG |
 | `openssl` | `rand [-hex\|-base64] [-out FILE] NUM` | Only `rand`; other subcommands fail with `Invalid command` |
+| `make` | `-f`, `-C`, `-n`, `-k`, `-q`, `-s`, `-i`, `-B`, `-e`, `-j` (sequential), `VAR=value` | GNU make subset; recipes run in the sandbox shell; no built-in implicit rules, `$(eval)` or `vpath` (L-MAKE-001..003) |
 | `curl` | `-s`, `-o`, `-X`, `-d`/`--data`, `--data-raw`, `--data-binary`, `--data-urlencode`, `-G`/`--get`, `-H`, `-I`, `-f`, `-L`, `-w`, `--compressed`, `-u`, `-A`, `-e`, `-v`, `-m` | HTTP client (requires http_client feature) |
 | `wget` | `-q`, `-O`, `--spider`, `--header`, `-U`, `--post-data`, `-t` | Download files (requires http_client feature) |
 | `time` | `[-p] [-f FORMAT] [-o FILE] [-a] [-v] [--] PIPELINE` | Reserved-word timing; elapsed/status/Bashkit counters are truthful, host CPU/RSS fields say `unavailable` |

crates/bashkit/docs/threat-model.md

@@ -115,6 +115,7 @@ through configurable limits.
 | Interactive terminal flooding (TM-DOS-119) | Unbounded type-ahead, undrained output, or a `vi` buffer grown by pastes | Caps on unread input (1 MiB), retained output (4 MiB), scrollback (1000 rows), transcript (1 MiB), line length, `vi` buffer (8 MiB) and undo history; `:w` goes through VFS limits | MITIGATED |
 | Input wait vs. timeout (TM-DOS-120) | Abusing the keyboard-wait exclusion to run work past the deadline | Only time blocked reading the terminal is excluded; CPU work and `sleep` still count | MITIGATED |
 | Concurrent pipeline amplification (TM-DOS-124) | An endless loop piped into `head`, a producer whose reader quit, or recursive pipelines `f() { f \| f; }` | 4 KiB pipes with backpressure; a writer whose reader is gone ends with 141 (SIGPIPE); streaming nesting counts toward `max_subshell_depth` and falls back to sequential stages past 4 levels; stages share the session budget, timeout and cancellation | MITIGATED |
+| make amplification (TM-DOS-126) | Exponential recursive variables, self-including makefiles, deep `$(MAKE)` recursion, huge graphs | Expansion depth 200 and 4 MiB per expansion; include depth 16; target, query and glob caps per run; `$(MAKE)` stops at level 8; recipes run under the session budget and timeout | MITIGATED |
 | Random generator amplification (TM-DOS-123) | `openssl rand` asked for gigabytes | Requests capped at 1 MiB; fixed-size `uuidgen`/`$SRANDOM` | MITIGATED |
 | Unbounded builtin output (TM-DOS-058) | `seq 1 1000000` produces 1M lines | Add `max_stdout_bytes` limit | **MITIGATED** |
 | Silent truncation at builtin caps (TM-DOS-109) | `seq 200000`, an awk loop past its cap, or an oversized `sprintf` expression returns incomplete output with exit 0 | Caps report `<cmd>: <what> limit (<N>) exceeded` on stderr and exit non-zero; awk caps and formatting errors are fatal | **MITIGATED** |

crates/bashkit/src/builtins/find/mod.rs

@@ -1003,10 +1003,12 @@ impl Builtin for Find {
         match run.next(None).await? {
             PlanStep::Done(result) => Ok(result),
             // Only reachable if the plan path was skipped; -exec needs it.
-            PlanStep::Run { .. } => Ok(ExecResult::err(
-                "find: -exec is not available in this context\n".to_string(),
-                1,
-            )),
+            PlanStep::Run { .. } | PlanStep::Capture { .. } | PlanStep::Emit { .. } => {
+                Ok(ExecResult::err(
+                    "find: -exec is not available in this context\n".to_string(),
+                    1,
+                ))
+            }
         }
     }
 

crates/bashkit/src/builtins/ls/mod.rs

@@ -1,6 +1,6 @@
 //! Directory listing builtins - ls, rmdir, and shared glob matching.
 
-mod glob;
+pub(crate) mod glob;
 mod list;
 mod rmdir;