chore: remediate UAT validation findings (DOC-007, R5, R6)

[marcuspat]

Addresses the Sentinel findings from the 2026-08-21 UAT and validation report.

Report findings

• DOC-007 (Medium) — license inconsistency. LICENSE is the MIT text and the README badge said MIT, but workspace.package.license declared Apache-2.0 and the README's License section said Apache-2.0. Reconciled to MIT. Verified with cargo metadata: all 8 crates now resolve to MIT.
• R5 — CONTRIBUTING.md. Setup, the 8-crate bounded-context map, code style, testing expectations (security-relevant changes need a test that demonstrates the deny path), ADR process, and the areas that get extra security review.
• R6 — release automation. Tag-driven release.yml: verify (clippy -D warnings, tests, cargo audit) → four-target binaries with SHA-256 sums (x86_64-unknown-linux-gnu, x86_64-unknown-linux-musl, aarch64-apple-darwin, x86_64-apple-darwin) → GitHub Release built from the matching CHANGELOG.md section → opt-in crates.io publish walking the workspace in dependency order.

Two blockers found while implementing R6

cargo publish would have rejected every crate. Workspace-internal dependencies were declared with path only:

sentinel-core = { path = "sentinel-core" }

Cargo requires a version on any dependency of a published crate, so R6's crates.io half was unachievable as written. Each now carries version = "0.1.0" alongside path.

CI is red on main today. The lint job runs cargo clippy --workspace --all-targets -- -D warnings; current stable emits 8 collapsible_match errors in sentinel-tui/src/event_handler.rs. The key handler now uses match guards.

Behaviour is deliberately unchanged. Converting KeyCode::Char('a') => { if tab == Plan { … } } to a guard makes non-Plan-tab presses fall through to the later KeyCode::Char(c) arm, which would start inserting a, s, and r into the goal input. An explicit no-op arm preserves the current swallow:

KeyCode::Char('a') | KeyCode::Char('s') | KeyCode::Char('r') => {}

Verification

Run locally against this tree:

Check	Result
cargo check --workspace --all-targets	pass
cargo clippy --workspace --all-targets -- -D warnings	pass
cargo test --workspace	pass — 413 tests
cargo metadata license resolution	MIT for all 8 crates

Every file on this branch was verified by git blob SHA against the locally built and tested tree.

Notes, not addressed here

• crates.io name. The README badge points at sentinel-agent, but no crate in the workspace has that name — the binary sentinel comes from sentinel-tui. The publish job publishes the eight real crate names; the badge needs a decision.
• rustfmt drift. cargo fmt --all -- --check fails across ~250 sites on current stable. CI does not run it and I left it out of release.yml rather than bundle a whole-tree reformat into this PR.
• Mojibake. Four files contain double-encoded UTF-8 in comments (� where ─ belongs). Cosmetic; a one-line sed if you want it.
• alpine:3.19 in the Docker runtime stage reached EOL in Nov 2025.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WhYNu2HEX62gqqtcPM5twr