refactor: split oversized hook.ts to respect 200 LOC limit

- Extract types to types.ts
- Extract constants to constants.ts
- Extract session ID helpers to session-id.ts
- Extract recovery logic to recovery.ts

hook.ts reduced from 331 to 164 LOC

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/compaction-context-injector/constants.ts

@@ -0,0 +1,5 @@
+export const HOOK_NAME = "compaction-context-injector"
+export const AGENT_RECOVERY_PROMPT = "[restore checkpointed session agent configuration after compaction]"
+export const NO_TEXT_TAIL_THRESHOLD = 5
+export const RECOVERY_COOLDOWN_MS = 60_000
+export const RECENT_COMPACTION_WINDOW_MS = 10 * 60 * 1000