fix(app): scope session page errors

[Brendonovich]

Summary

• Add an ErrorBoundary inside the session page main panel when new layout designs are enabled, so session load errors do not take down the tab shell.
• Move target session route resolution into the session page module so target-route failures render inside the session panel frame.
• Render known session-not-found errors with a stackless not-found panel instead of the generic stack trace error page.
• Include the server name, missing session ID, and a Close Tab action in the not-found panel.
• Style the session ID like markdown inline code and keep the server name as regular faint text.
• Keep session tab metadata fetch failures local to the tab strip and render Unknown Session instead of hiding the tab.
• Reset the boundary when switching session tabs.

[andrei-hasna]

Task-triggered merge review completed for PR #34254.\n\nValidation:\n- GitHub checks are green: check-compliance, check-standards, e2e linux/windows, nix-eval, typecheck, unit linux/windows.\n- Branch is fresh against dev: base ae53163, head 4524101.\n- Local merge-tree against origin/dev succeeded with no conflicts.\n- Clean temp worktree validation passed: app typecheck, targeted i18n/server-errors tests, focused lint with 0 errors, and app production build.\n- Independent adversarial reviewer found no merge blockers; residual risk is lack of dedicated UI regression coverage for the new session error fallback / Unknown Session tab behavior.\n\nMerge blocker:\n- Attempted squash merge pinned to reviewed head SHA 4524101, but GitHub rejected it: authenticated user andrei-hasna lacks MergePullRequest permission on anomalyco/opencode.\n\nNo files were mutated in the main checkout by this review.

[andrei-hasna]

Task-triggered merge review refreshed for PR #34254.

Current state checked on 2026-06-28:

• PR is open, not draft, MERGEABLE / CLEAN.
• Head: 4524101 (session-error-boundary).
• Current dev: 61a7f6d, newer than PR metadata base ae53163.
• GitHub checks are passing: check-compliance, check-standards, e2e linux/windows, nix-eval, typecheck, unit linux/windows.
• Local synthetic merge into current dev succeeded with no conflicts.
• Local validation in /tmp/opencode-pr34254.YX5OEY passed: bun run --cwd packages/app typecheck; bun test --preload ./packages/app/happydom.ts ./packages/app/src/utils/server-errors.test.ts (12 pass); focused oxlint on changed files (0 errors); bun run --cwd packages/app build.
• Secret-pattern scan on the PR diff found no configured token patterns.
• Independent adversarial reviewer found no merge blockers.

Merge blocker:

• Pinned squash merge attempt failed: GraphQL reported that andrei-hasna does not have permission to execute MergePullRequest. The authenticated account has READ permission on anomalyco/opencode, so this worker cannot complete the merge.

No files were mutated in the main checkout by this review.

[andrei-hasna]

Task-triggered merge review refreshed for PR #34254 on 2026-06-28.

Current state:

• PR is open, not draft, and GitHub reports MERGEABLE / CLEAN.
• Head: 4524101 (session-error-boundary).
• Current dev: dfeb1b5.
• GitHub checks are passing: check-compliance, check-standards, e2e linux/windows, nix-eval, typecheck, unit linux/windows.
• Local synthetic merge into current origin/dev succeeded with no conflicts.
• Local validation in a clean temp worktree passed:
  • bun run --cwd packages/app typecheck
  • bun test --preload ./packages/app/happydom.ts ./packages/app/src/utils/server-errors.test.ts (12 pass)
  • focused oxlint on changed files (0 errors, existing warnings only)
  • bun run --cwd packages/app build
• Secret-pattern scan on the PR diff found no configured token patterns.
• Independent adversarial verifier found no merge blockers.

Residual non-blocking risk:

• titlebar-tab-strip.tsx currently treats any session.resolve() failure as missing, so a transient network/server/auth failure can show Unknown Session. Tracked separately as follow-up; not a merge blocker for this PR.

Merge blocker:

• The authenticated account andrei-hasna has READ permission on anomalyco/opencode; GraphQL reports viewerCanUpdate=false and viewerCanMergeAsAdmin=false. This worker cannot merge PR fix(app): scope session page errors #34254.

No files were mutated in the main checkout by this review.

[andrei-hasna]

OpenLoops merge review for task ae9bc65e is ready but blocked by permissions.

Validation completed on current dev:

• Live PR state: OPEN, MERGEABLE/CLEAN, all GitHub checks green.
• PR head: 4524101. Current dev checked locally: 58ba99e. The branch is behind dev, but a local no-commit merge onto current dev applied cleanly.
• bun install --frozen-lockfile passed.
• From packages/app: bun run typecheck passed.
• Focused app unit tests passed: bun test --preload ./happydom.ts ./src/utils/server-errors.test.ts ./src/i18n/parity.test.ts ./src/components/titlebar-tab-gesture.test.ts ./src/context/tabs.test.ts (18/18).
• bun run build passed with existing Vite chunk/dynamic-import warnings.
• Production first-navigation benchmark was run before and after this PR with PLAYWRIGHT_WORKERS=1 bunx playwright test --config e2e/performance/playwright.config.ts timeline/first-navigation-benchmark.spec.ts; both runs passed 3/3 with zero blank/unknown samples.
• Read-only adversarial review: PASS, no merge blockers. Residual risk noted: the new-layout panel boundary will also render inline fallback for future programming errors inside the panel.
• Staged secret scan and git diff --check passed.

Merge attempt used a head-SHA guard and failed only because active GitHub user andrei-hasna lacks MergePullRequest permission on anomalyco/opencode:

gh pr merge 34254 --repo anomalyco/opencode --squash --subject "fix(app): scope session page errors" --body "" --match-head-commit 4524101689fc164d1b0138d278815e07981f4ff5

Follow-up todos task 445aa140-3781-4b9b-a765-4d092807de36 tracks merge by an authorized GitHub identity. Please rerun a final live status/head check before merging if the head changes.