Task: Recover Pi integration and merge updater fix

Identity

Recover the abandoned Pi integration documentation already present in the main worktree and validate it against the completed Pi source-task records.
Integrate the updater downgrade-prevention change from source commit 2e61800fed793b63b3b7804a03a4c7d8617e23d7 into main.
Verify the focused updater behavior, type safety, lint, and production Vite build before handing back the integrated branch.
Preserve unrelated untracked task records byte-for-byte and outside this task's commits.

User explicitly authorized force-releasing and taking over the abandoned Pi integration task.
Treat completed source task records as read-only evidence; promote only the canonical Pi documentation that is supported by those records.
Keep unverified Pi release gaps explicit: real Provider execution, macOS x64/arm64 packaged artifacts, and native non-WSL Linux remain unverified.
Apply only the two updater source/test changes from the verified feature commit so the feature task record remains source-owned.
Do not modify, delete, or commit 20260819-package-learning-off-115-9c4d.md or the superseded Pi integration task record without separate authority. After the user granted that authority, move both files byte-for-byte to a repository-external recovery directory.

Validate the pending Pi canonical documentation against source-task facts and current product boundaries.
Apply the verified updater downgrade guard and its focused regression tests.
Run focused tests, typecheck, scoped lint, and build:vite; inspect the final diff and commit the integrated result on main.
Run the Task Documentation Gate, release ownership, and report any remaining foreign-record blocker without weakening or bypassing the gate.

Recovered and semantically reviewed the pending Pi canonical documentation against the completed hard-cutover, provider, release-proof, legacy-removal, and background-run source tasks.
Integrated the exact updater source/test change from 2e61800fed793b63b3b7804a03a4c7d8617e23d7 into main without copying or editing its source-owned task record.
Automatic update channel selection and later channel changes now explicitly restore autoUpdater.allowDowngrade = false, preventing installed 2.0.0 from treating online 1.1.9 as an available update.
Preserved both unrelated/unregistered task records byte-for-byte and moved them to D:\Datas\OthersProjects\makelore-task-record-recovery-8f3a6c21, outside the repository and the integration commits.

Exact source parity: git diff --exit-code 2e61800 -- electron/main/updater.ts tests/unit/app-updater.test.ts passed before task-record finalization.
pnpm exec vitest run tests/unit/app-updater.test.ts: passed, 1 file / 15 tests.
pnpm run typecheck: passed.
pnpm exec eslint electron/main/updater.ts tests/unit/app-updater.test.ts: passed.
pnpm test: passed, 181 regular files / 1543 tests passed / 2 skipped, followed by the pressure file with 1/1 passed.
pnpm run build:vite: passed for Renderer, Electron Main, Preload, and the release utility worker; existing dynamic-import and large-chunk warnings remain warnings only.
git diff --check: passed.
check_doc_drift.py --task-id 20260826-recover-pi-updater-integration-8f3a6c21: passed after the user-authorized recovery move; all project-document changes satisfy integration ownership boundaries.

The two recovered task records remain available outside the repository at D:\Datas\OthersProjects\makelore-task-record-recovery-8f3a6c21; restore them only if a future task establishes the correct owner and destination.
Real Provider execution, packaged macOS x64/arm64 artifacts, and native non-WSL Linux artifacts remain explicitly unverified Pi release gates.

Applied the already-supported Pi hard-cutover facts to the canonical success criteria, decision index/ADR, architecture, current state, business rules, evidence index, and commitments.
No additional updater promotion candidate: the updater behavior is captured by focused tests and does not change an architectural boundary.