Add unified exec plugin lifecycle adapter

[kmbroai]

Responsibility

Integrate the dormant core plugin-script lifecycle tracker from #27369 into local unified-exec spawn lifecycle handling while preserving unified-exec's existing generic spawn lifecycle.

Boundary

This slice adapts codex-rs/core/src/tools/runtimes/unified_exec.rs plus the required cross-platform SpawnLifecycle re-export in codex-rs/core/src/unified_exec/mod.rs: it resolves attribution from the original hook_command/cwd/shell_type, composes local unified-exec lifecycle callbacks, and keeps generic lifecycle callback ordering first. Shell/zsh runtime lifecycle work remains the sibling boundary and is deliberately not included here.

Dependency

Depends on #27369 (dev/kyleb/plugin-script-lifecycle-metrics) at exact head db17b99fbe5c1323856e9e2eebcad720cdddf4af.

Deliberately deferred / excluded

• Remote exec-server commands remain unattributed and unwrapped because local roots/cwd cannot safely attribute remote execution.
• Shell/zsh runtime-specific integration remains outside this unified-exec sibling.
• No UI evidence: this is lifecycle analytics plumbing only; no user-visible UI changes.

Size

281 changed lines total (278 additions, 3 deletions), two intended handwritten files.

Validation

• cd codex-rs && just test -p codex-core unified_exec — focused/new runtime tests passed, but required command failed locally in suite::unified_exec::unified_exec_runs_under_sandbox with empty sandbox output; rerun required in CI.
• cd codex-rs && just test -p codex-core plugin_script_lifecycle — passed.
• cd codex-rs && just argument-comment-lint — passed.
• cd codex-rs && just fix -p codex-core — passed.
• cd codex-rs && just fmt — passed.
• Require exact-head Windows/Bazel CI before review/merge because unified-exec compiles cross-platform.

Tracking

• Claim: CLAIM_KEY=linear_issue:FOO-574, CLAIM_ID=claim-1a4aebf2007e42c1b03e896787970de3
• Sticky worker: kyleb-worker-0

Stack position

Slice 7/7 in FOO-574 merge order; direct dependency: #27369.

[chatgpt-codex-connector]

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