Harden addon test and release gates

[nicodes]

Self-verification evidence (Team No Review)

• Issue / criteria: fieldsofrevik#144 — truthful fail-safe Godot/package/release gates.
• Source: aviorstudio/gd-gesture, a04-gate, exact head 1290e5b59d820f6d42d32a460c63297371f49a86; baseline 530a78d6feba083fe37865a82ca44d0abf5132e6.
• Scope: Godot runner, immutable Godot/action identities, deterministic package validator, installed-byte editor lifecycle, least-privilege release split, README correction. Non-goal: gesture behavior (next stack layer).
• Versions: Godot 4.7.2.stable.official.ed1daf0bf; Python 3.13; Linux; SHA-512 engine identity in tools/godot-release.json.
• Gate controls: 12 runner controls observed runtime-error-with-zero-exit, overwritten assertion, parse/load failure, timeout, missing executable/sentinel, and duplicate sentinel fail; restored fixture passed once. Package traversal, symlink, missing and unexpected-member controls failed as required. Actual PR runs demonstrated the malformed literal concurrency key canceling Harden addon test and release gates #10 when Implement per-pointer gesture cancellation #11 started; ci-${{ github.ref }} restored independent reachable runs.
• Reachability: restored suites emitted exactly one PASS gd-gesture <suite> assertions=<count> sentinel; missing/duplicate sentinels fail.
• Package: closed 9-file manifest; no symlink/traversal/test roots. Local exact-layer ZIP SHA-256 cee97245076ac8ffa7da4483427ae94a63e259bb6d34a6678ee6cf8c3a29fefa; installed-tree SHA-256 3b40ce7638378a4295ecc0ab33a44a5812abfd4d7854f188452ca9927becb793.
• Lifecycle: clean ZIP install; actual headless editor enable; editor restart; packaged module smoke; disable; restart/cleanup; consumer-owned GdGesture preserved. PASS.
• Commands: RUNNER_TEMP=/tmp/opencode ... ./tools/setup_godot.sh; GODOT_BIN=... ./tests/test.sh; python3 tools/package_addon.py; GODOT_BIN=... ./tests/package_lifecycle.sh; per-test timeout 30s, process-control timeout 0.25s.
• Supply chain: Godot archives checksum-verified; gdam-actions install/publish pinned to d735444eb470194585def44521d5d91df2260e63; PR permissions read-only and credentialed publication isolated.
• Exact-head CI: PASS — run 34718364705 at 1290e5b59d820f6d42d32a460c63297371f49a86.
• Browser evidence: N/A to the gate-only layer; the dependent behavior layer exports and personally verifies the packaged web playground.
• Untested/residual: macOS, Windows, and mobile runners are outside the approved D-14 matrix. Release/GDAM publication is post-merge and blocks issue completion.