Add persistent disk cache for parsed session data

Cache normalized turns/calls to ~/.cache/codeburn/session-cache.json so
the CLI skips re-parsing unchanged JSONL files on subsequent runs.
File reconciliation uses dev+ino+mtime+size fingerprinting; cost,
classification, and summaries are recomputed at query time. Atomic
writes via temp+fsync+rename, deep structural validation on load,
per-provider env fingerprinting, and best-effort save so cache failures
never break the CLI. ~6x speedup on warm cache.

src/types.ts

@@ -83,6 +83,7 @@ export type ParsedApiCall = {
   timestamp: string
   bashCommands: string[]
   deduplicationKey: string
+  cacheCreationOneHourTokens?: number
 }
 
 export type TaskCategory =