fix(sharing): stabilize local identity bootstrap

[kunickiaj]

Description

Adopt the stable device-backed identity before invite defaults or local profile projection. Retire stale local:local fallback identities safely, preserve foreign-origin ownership, and add the approved dogfood stabilization design/plan plus fixture invariants.

Closes codemem-h2wu.

Type of Change

• 🚀 Feature (new functionality)
• 🐛 Bug fix (fixes an issue)
• 📚 Documentation (docs-only change)
• 🔧 Maintenance (refactor, chore, CI, etc.)
• 🧪 Testing (test-only changes)

Testing

• Relevant checks pass locally (pnpm run tsc, pnpm run lint, pnpm run test)
• Added/updated tests for changes
• Manually verified changes work as expected

Focused identity/store/viewer/dogfood tests passed. The complete stack passed pnpm run check with 3,207 tests.

Checklist

• Code follows project style (pnpm run lint passes for touched files)
• Self-review completed
• Documentation updated (if needed)
• No new warnings introduced

[kunickiaj]

• fix(sharing): clarify recipient access dialogs #1353 : 2 dependent PRs (#1354 , #1355 )
• fix(sync): show truthful primary status #1352
• feat(sharing): accept project invites in Sharing #1351
• fix(sharing): make project acceptance truthful #1350
• fix(sharing): stabilize local identity bootstrap #1349 👈 (View in Graphite)
• main

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[kunickiaj]

Merge activity

• Jul 24, 9:40 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jul 24, 9:40 PM UTC: @kunickiaj merged this pull request with Graphite.