fix(manage): preserve Codex SessionStart by injecting per-event hooks

[anthony-chaudhary]

Parent: #11555 / #11616 context reduction dogfood. Live managed Codex Astra dispatch fails before model execution: manage_parity.go injects hooks={Stop,...}, and guardCodexSessionStartConfigCollision correctly refuses a whole-table hooks override. Outcome: retain Stop, PreCompact, PreToolUse, PostToolUse managed handlers while preserving guarded SessionStart and its trust state. Minimal scope cmd/fak/manage_parity.go and its existing test. Witness: run actual managed-hook installation through guard SessionStart collision validation and assert all four event handlers survive; then retry bounded live Codex dispatch. Do not weaken collision or trust guards. For operators running guarded Codex workers; enabling all-in-one workflow; next-best is a launch that fails before doing work. Captured private log referenced by _scratch/astra-context-continuation/dispatch-live.json; no private log contents to publish.

[anthony-chaudhary]

Atomic reproduction witnessed RED: TestInstallManagedNativeHooksUsesSupportedSeams fails at actual guard SessionStart collision. Minimal per-event hook configuration now passes same WSL test (package output ok 0.075s; final wrapper exit pending). No guard weakening. Two files preserved; managed worktree git administrative directory disappeared during testing, so no landing claim. Recover managed checkout before commit/land, then retry real dispatch. Parent 3x result remains unproven.