fix(config): preserve native literal build paths

[roodboi]

Native builds whose context contains literal dollar expressions can fail when Compose translates the path into Bake expressions. The supported context/Dockerfile/target subset now uses direct Buildx arguments under the existing generation owner, preserving path bytes and producing exact owned image tags. Compose consumes those images without rebuilding.

The owner rechecks source, image identity, cancellation and deadlines around build effects. Omitted build policy reuses a qualified image; explicit rebuild changes it. Cold one-off commands build their target and dependencies; saved routed one-off commands preserve running dependencies and routes. Failures retain pending recovery state. Advanced build options, secrets and SSH are refused before hooks or engine effects.

Validation at 9799f4a6:

• Independent source review, typecheck, lint, privacy and current-branch build passed.
• Full local suite: 3,643 passed, 73 documented skips, zero failures.
• All 12 CI jobs passed; Docker E2E passed all 25 scenarios without skips.
• Final current-executable M3 acceptance passed in 34.9s, covering literal paths, Dockerfile/target selection, reuse/rebuild, retained data and exact image/resource cleanup. Fresh preflight/postflight preserve every original resource identity and volume creation time.
• A separately pinned earlier build interruption proved observed host process-group exit and explicit recovery of the same retained fixture; it is not a final-head guest-worker reaping test.

Ordinary BuildKit cache remains retained. This change does not claim cache reclamation, advanced-option parity or a measured performance improvement.