fix: prevent cross-project knowledge entries from leaking into AGENTS.md

[BYK]

Problem

Cross-project knowledge entries from unrelated projects were appearing in a project's AGENTS.md (reported on getsentry/devinfra-deployment-service#832). Entries like "Consola prompt cancel returns truthy Symbol", "Zod z.coerce.number() converts null to 0", and "Craft v2 GitHub App must be installed per-repo" appeared in devinfra-deployment-service's AGENTS.md — none of which are relevant to that repo.

Root Causes

Three interrelated issues:

1. Curator creates project-scoped duplicates: The curator saw all cross-project entries via ltm.forProject(path, cfg.crossProject=true), then the LLM created near-duplicates scoped to the current project. The title dedup guard only checked same project_id, missing cross-project originals.

2. importFromFile defaults crossProject to true: Entries imported from AGENTS.md got crossProject: true (the ltm.create() default), leaking them into other projects' system prompts.

3. Consolidation count inflated: ltm.forProject(projectPath) included cross-project entries from all repos, triggering unnecessary consolidation.

Fix

Source changes (5 files)

• src/curator.ts: Curator and consolidation now use forProject(path, false) — only see project-specific entries
• src/ltm.ts:
  • Default crossProject changed from true to false in create()
  • Dedup guard extended to also check cross-project entries by title
  • forProject(path, false) no longer includes project_id IS NULL entries
• src/index.ts: Consolidation count uses forProject(path, false)
• src/config.ts: crossProject config default changed to false
• src/agents-file.ts: Both import paths explicitly set crossProject: false

Backward compatibility

• forSession() is unaffected — it has its own SQL queries with relevance gating for cross-project entries, so they still appear in system prompts when relevant
• Existing cross-project entries remain in the DB and accessible via forSession()

Tests

7 new tests added covering:

• create() defaults crossProject to false
• Dedup guard catches title matches against cross-project entries
• importFromFile creates entries with cross_project = 0
• Cross-project entries don't appear in exportToFile output
• Cross-project entries don't inflate forProject(path, false) count

All 194 tests pass (187 existing + 7 new).