docs: update coverage objectives and architecture in PLANS.md

Author: chrisgleissner

PLANS.md

@@ -2,21 +2,26 @@
 
 ## Objective
 
-Raise Codecov-reported overall coverage (README badge metric) from ~80% to >=95% while preserving correctness and keeping CI green.
+Raise Codecov-reported merged coverage (unit + Playwright E2E LCOV, uploaded via CI to Codecov) to >=90% for both lines AND branches. CI gate (`scripts/check-coverage-threshold.mjs`) enforces both thresholds on `coverage/lcov-merged.info`.
 
-## Baseline Snapshot (Codecov-relevant, merged web coverage)
+## Coverage Architecture
 
-Collection command: `PLAYWRIGHT_PORT=4273 npm run test:coverage:all`
+- **Unit LCOV** (`coverage/lcov.info`): generated by `npm run test:coverage` (Vitest v8). Covers 81 source files. Uploaded as CI artifact to `web-coverage-merge` job.
+- **E2E LCOV** (`coverage/e2e/lcov.info`): generated by `npx nyc report` from `.nyc_output/` JSON collected during Playwright runs (Istanbul instrumentation). Covers 259 source files (all of `src/**`).
+- **Merged LCOV** (`coverage/lcov-merged.info`): produced by `npx lcov-result-merger` combining both LCOVs. Uploaded to Codecov. CI checks BOTH line AND branch >= 90%.
 
-- Unit LCOV (`coverage/lcov.info`):
-  - Line: 94.35% (5580/5914)
-  - Branch: 90.16% (2153/2388)
-- Playwright E2E LCOV (`coverage/e2e/lcov.info`):
-  - Line: 71.98% (11235/15609)
-  - Branch: 57.74% (5037/8724)
-- Merged LCOV uploaded to Codecov (`coverage/lcov-merged.info`):
-  - Line: 80.81% (14767/18274)
-  - Branch: 64.87% (7195/11091)
+## Baseline Snapshot (March 2026 — current branch)
+
+- Unit LCOV (`coverage/lcov.info`, 81 files):
+  - Line: 94.51% | Branch: 90.30%
+- E2E LCOV (from `.nyc_output/`, 259 files):
+  - Line: 72.00% (11238/15609) | Branch: 57.81% (5043/8724)
+- **Merged LCOV** (263 files, what CI enforces and Codecov reports):
+  - **Line: 81.11%** (14864/18326) | **Branch: 64.95%** (7247/11158)
+
+**Gap to close to reach >=90%**:
+- Lines: need 1629 more covered (14864 → 16493)
+- Branches: need 2795 more covered (7247 → 10042) — the harder constraint
 
 ## Coverage Propagation Model (what affects README/Codecov)
 
@@ -39,7 +44,7 @@ Collection command: `PLAYWRIGHT_PORT=4273 npm run test:coverage:all`
 
 ## Lowest-Coverage Files (ranked)
 
-1. `src/lib/diagnostics/networkSnapshot.ts` — 5.71% / 0.00%
+1. `src/lib/diagnostics/networkSnapshot.ts` — 92.85% / 100.00% (Previously 5.71% / 0.00%)
 2. `src/pages/home/components/MachineControls.tsx` — 14.29% / 84.62%
 3. `src/lib/config/settingsTransfer.ts` — 14.67% / 0.00%
 4. `src/lib/diagnostics/webServerLogs.ts` — 17.65% / 6.25%