feat(cursor-agent): discover and reconstruct sessions from store.db (fixes #986)

[maheshsingh20]

Summary

Fixes #986.

The cursor-agent provider previously missed CLI sessions stored in ~/.cursor/chats/**/store.db. This PR adds full discovery and reconstruction for those sessions, with proper source precedence, deduplication, WAL-aware caching, and blobEncryptionKey redaction.

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Changes

src/providers/cursor-agent.ts

Discovery

• discoverSessions() now scans ~/.cursor/chats/<hash>/<uuid>/store.db before the existing transcript walk, without following symlinks beyond two directory levels.
• probeRoots() gains a chats entry so codeburn doctor reports it.

Schema validation

• Checks for required meta + blobs tables before any data is read. A missing or incompatible schema emits a warning and falls through to the transcript fallback.

Metadata decoding

• meta['0'] is hex-decoded from UTF-8 JSON to extract agentId, latestRootBlobId, name, createdAt, and lastUsedModel.
• blobEncryptionKey is explicitly excluded from the decoded object and never appears in logs, caches, exports, snapshots, emitted calls, or stderr output.

Blob-graph reconstruction

• BFS walk from latestRootBlobId, following nextBlobId chains and childBlobIds arrays.
• Classifies blobs by role (user / assistant / model / request).
• Handles both plain text strings and content-block arrays ([{type:'text', text:'...'}]).
• Handles both toolCalls: [{name}] and content-block {type:'tool_use', name} formats.
• Unknown fields are silently ignored for forward compatibility.

Token provenance

• Explicit per-request inputTokens / outputTokens used when present and plausible (<=2,000,000). Values above that threshold are treated as context-window gauges and replaced by char-based estimates.
• cacheCreationInputTokens and cacheReadInputTokens recorded when present.
• costIsEstimated: true set on any call where at least one count was estimated.

Timestamps

• Internal blob/request timestamps preferred; session createdAt used as session-level fallback. File mtime is never reported as an exact request timestamp.
• Both epoch-ms (> 1e12) and epoch-s (< 1e12) values are normalised correctly.

WAL-aware in-memory cache

• Per-session cache keyed on a fingerprint combining store.db mtime and the -wal sidecar size/mtime. Active sessions always trigger a re-parse when the WAL changes.

Source precedence and deduplication

• store.db sources are emitted first in discoverSessions().
• A successfully decoded store records a cursor-agent-store-decoded:<uuid> sentinel in seenKeys; transcript parsers for the same session UUID check it and skip themselves.
• A store that fails schema/metadata validation does not set the sentinel, so the JSONL/TXT transcript fallback runs normally without double-counting.

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tests/providers/cursor-agent-store.test.ts (new, 44 tests)

Category	Tests
Discovery	Empty/missing chats dir, valid store found, multiple sessions, non-UUID dirs skipped, no store.db skipped, probeRoots
Valid minimal store	Single-turn parse, model resolution, costUSD > 0
Multi-turn blob graph	3-turn nextBlobId chain, childBlobIds branching, stable dedup keys, seenKeys respected
Malformed metadata	Bad hex, invalid JSON, missing agentId, short blobId, agentId mismatch, missing meta table, missing blobs table
Missing/invalid blobs	Absent root blob, broken nextBlobId (partial graph still yields), corrupt blob JSON
Unknown fields	Ignored without crash, content-block array format, toolCalls array format
Timestamp normalization	Epoch-ms, epoch-s promoted to ms, session-level fallback
Token provenance	Exact both, input estimated, output estimated, gauge rejected, cache tokens, all absent
Store + transcript dedup	One set of calls per session UUID, transcript fallback on corrupt store, store-only session appears
WAL cache	Re-parse on file change, cache hit on unchanged fingerprint
blobEncryptionKey redaction	Absent from emitted calls, absent from stderr, absent from source paths

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Test results

Tests  44 passed  <- new (cursor-agent-store.test.ts)
Tests  17 passed  <- existing cursor-agent.test.ts, no regressions