fix: bound large-repo memory and traversal work

[danusha2345]

Summary

• bound resolver and C function-pointer synthesis caches by retained bytes, release pass-local facts early, and merge sequential synthesis results incrementally
• reject oversized package targets before UTF-8 decoding, preventing HarmonyOS .har archives and similar dependency blobs from exhausting V8 heap during resolution (Daemon OOMs (~4 GB heap) on small project during startup catch-up sync; stale daemon.pid + OS PID reuse then blocks all daemon restarts (unlock does not help) #1553)
• replace repeated source-prefix scans in dynamic-dispatch synthesis with linear line lookup (folded from fix: avoid quadratic synthesis line lookups #1580)
• recycle a loaded query-worker burst to one fresh worker after 60 seconds idle
• make shortest-path BFS linear and bound impact traversal at SQL level with explicit MCP truncation
• release tag-based CFML parse trees and prune Linux watchers for removed directory subtrees
• apply the existing WAL pressure valve during incremental changed-file storage and both batched resolution paths; this wires the containment hook that sync() missed without claiming the reported 64 GiB incident is fully reproduced (v1.5.0: codegraph.db-wal grew to 64 GiB and filled disk on a Linux-kernel-sized repo #1539)
• let MCP and its shared-daemon key adopt exactly one indexed child beneath an unindexed workspace/git root; when there are zero or several candidates, emit actionable diagnostics and never guess (MCP server ignores indexed sub-projects below cwd #1606, MCP server is silent when no project resolves #1607)
• merge current upstream main (44e1812) while preserving all fork fixes

Validation

• full suite: 191 test files, 3,198 passed, 9 skipped
• TypeScript build passes
• focused WAL regression proves sync() invokes backpressure during changed-file storage and orphan resolution: 21/21
• focused MCP/root regressions exercise a real spawned server: one child is opened as default, multiple children are listed, and no-index startup explains that live sync is disabled: 51/51
• self-index after the merge/fixes: 594 files, 12,968 nodes, 46,041 edges, 0 pending refs, 0 pending changes, 0-byte WAL
• native kernel build and earlier focused archive/quadratic-synthesis regressions pass
• 290 MB sparse .har probe: rejected before decode, 58 MB peak RSS, 0.05 s
• ArduPilot full index (13,633 files): peak PSS reduced from 4.09-4.26 GB to 3.316 GB with resolver workers disabled
• ArduPilot graph remained identical to baseline: 177,869 nodes / 474,074 edges
• 100,000-node shortest path probe: 0.14 s, ~119 MB max RSS

Commits are separated by defect for review.