fix: /api/reports returns empty for DB-persisted sessions on new instances

[Number531]

Problem

The /api/reports?session= endpoint serves artifacts exclusively from the local filesystem (reports/ directory + exports.json manifest). On new GCE instances created by MIG auto-healing or zone migration, the reports/ directory is empty — all artifacts from previous sessions exist only in the PostgreSQL report_artifacts table (persisted since v4.9.0).

Result: PDFs, DOCXs, charts, and Markdown files show "no documents available" for any session run on a prior instance, despite 309 artifacts across 5 sessions being present in the database.

Root Cause

/api/reports checked fs.existsSync(sessionPath) and returned { reportCount: 0, reports: [] } immediately when the directory was missing, never querying the database. The DB artifact endpoints (/api/db/artifacts/:id/download, /api/db/sessions/:sessionKey/artifacts) existed but were not wired into the reports flow that the frontend consumes.

Fix (v4.12.2)

• DB fallback branch in claude-sdk-server.js: when filesystem session directory is missing, queries report_artifacts joined on sessions.session_key and returns artifacts with /api/db/artifacts/:id/download URLs
• PDF inline disposition in dbFrontendRouter.js: PDFs served with Content-Disposition: inline to match existing /api/convert/download behavior (opens in-browser tab)

Files Changed

• src/server/claude-sdk-server.js — DB fallback in /api/reports
• src/server/dbFrontendRouter.js — PDF inline disposition
• CHANGELOG.md — v4.12.2 entry

Verification Checklist

• Commit and push to worktree-deploy-week-4
• Rebuild Docker image and push to Artifact Registry
• Rolling update on staging MIG
• Load March 13 session (c3a5ed55) in browser — verify PDFs/DOCXs/charts populate
• Verify PDF opens in new tab (inline disposition)
• Verify current-session filesystem artifacts still load normally
• Verify health endpoint returns 200

Labels

bug, deploy-week-4, database