feat(action): harden defaults and proxy lifecycle

[activadee]

What changed

This PR hardens the composite action's defaults and runtime behavior across CLI install, proxy lifecycle checks, argument parsing, permission gating, and proxy config management.

User-facing impact

Before this change, action runs could incorrectly trust stale proxy server-info files, parse malformed JSON codex-args without validation, and write duplicate/legacy proxy config entries over repeated runs. Bot bypass behavior also differed between code paths, creating surprising access-control behavior.

With this change:

• model now defaults to gpt-5.3-codex while allowing opt-out with model: "".
• codex-version defaults to 0.104.0 for deterministic installs, while empty input still resolves to latest.
• proxy startup now probes liveness and restarts unhealthy/stale instances.
• proxy config writes are idempotent and managed-block based.
• codex-args JSON parsing now enforces a JSON array of strings.
• bot bypass defaults align to allow-bots=false consistently.
• CI now runs tests and workflow lint checks.

Root causes addressed

• Proxy readiness previously inferred health from file presence alone, which allowed stale state.
• Extra-arg parsing accepted raw JSON parse output without structural validation.
• Proxy config mutation relied on append/prepend behavior instead of robust managed-block reconciliation.
• Legacy block stripping could consume unrelated TOML sections when next headers were array/commented forms.

Fix details

• Added probe-proxy command and port reachability checks via src/probeProxy.ts.
• Updated action workflow to probe/restart and verify proxy health before use.
• Introduced parseExtraArgs helper with strict JSON-array/string validation and tests.
• Refactored writeProxyConfig to render managed blocks idempotently and strip legacy blocks safely.
• Extended TOML header detection to recognize [table], [[array_table]], and inline-comment headers to avoid accidental config loss.
• Updated permission-check defaults and tests for bot handling.
• Added/updated tests for new parsing, proxy probing, permission behavior, and proxy-config regression coverage.

Validation

• pnpm test (18 passing tests)
• pnpm run build

[github-actions]

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