Connect Add Column to Sources

[3mdistal]

Problem

Content databases can already connect Builder, Notion, local tables, and local-folder Sources, but that capability is hidden in database settings. Someone adding a column has no obvious route to discover source-backed fields, so the existing Source model feels like separate database machinery instead of a natural way to add data.

Approach

Add one small handoff from the existing Add column menu into the existing Sources UI. A successful connection returns to the database with Add column open and the newly available fields grouped under From [source]. Closing Sources is a true cancel: it returns to the database without reopening Add column or mutating a connection.

This PR deliberately does not add source suggestions, relationship matching, formula UI, or a separate “add property from this source” workflow. The existing Sources UI remains responsible for choosing and connecting a source.

What changed

• Added a localized Connect a source entry to Add column, including localized search matching.
• Reused the database’s existing Sources panel and attach actions instead of introducing another connection surface.
• Added an acknowledged, monotonic handoff request so Add column reopens after each successful connection, including across database refresh/remount behavior, without reopening after cancel.
• Suppressed the Add column popover's exit animation only during the Sources handoff so the two surfaces never appear stacked; ordinary open/cancel behavior is unchanged.
• Reused the existing source-field grouping and optimistic source-field property mutation for From [source] fields.
• Generalized local-primary bootstrap for read-only detail Sources so a normal local database remains the primary side before a detail Source is attached.
• Added focused regression coverage for cancel/no-mutation, repeated successful handoffs, localized search, handoff animation cleanup, and local-primary bootstrap, plus a user-facing changelog entry.

Safety and operations

• No schema migration, new route, credential path, feature flag, or production-data operation is introduced.
• Source connection still goes through the existing typed action surface and existing Sources UI.
• The detail-source bootstrap creates the same local source snapshot already used for Notion details; the broader condition preserves local-primary semantics for any supported details Source and composes with current source-mutation locking.
• Rollback is limited to the Add column handoff, its focused source-bootstrap condition, tests, translations, and changelog entry.

Verification

Exact repaired head: 0c30726392256c8c7711dc367fbe439cb0dd92c5, refreshed onto current main at 86ea1866721a64527b412cd43ad32428e490f4a9.

• 86 focused tests passed across Add column behavior, translated search, source actions, and database UI regressions.
• 200 Content database tests passed, including the current migration and locking-sensitive database suite.
• Full Content suite passed: 170 files passed, 2 skipped; 2,120 tests passed, 3 expected failures, and 18 skipped.
• Content typecheck passed on the repository-pinned Node 24 runtime.
• Repository guards passed 50/50.
• Content product-impact policy passed with a valid local_refinement declaration and no deterministic findings.
• git diff --check passed.
• Independent exact-head technical review found no issues. The reviewer verified the handoff-only animation suppression and its reset behavior, cancel/retry handling, repeated-success path, and the absence of boundary expansion.
• Independent exact-head real-interface QA passed the complete frozen H1–H7 story: Add property entry; clean handoff to existing Sources with no stacked popover; cancel/no-new-connection; existing source selection and match review; confirmation; Add property reopened; exact From QA Books 2662 grouping with federated fields. No console or page errors were observed in the successful run.
• Alice's prior product/interaction acceptance remains the governing boundary: existing Sources UI, no suggested-sources expansion.
• Current-head GitHub checks are green except Fast tests lane-2 and its aggregate. The lane failed identically on its one bounded rerun because packages/docs/server/plugins/agent-chat.spec.ts could not import the generated packages/docs/.generated/actions-registry.js; the other 161 tests in that package run passed. This PR changes no Docs or CI-generation files, so that unrelated base/workflow defect is intentionally not folded into this stack base.

Review focus

• Does the one-shot handoff preserve the intended difference between cancel and successful connection, including repeated connections and remounts?
• Does generalizing local-primary bootstrap keep detail-source attachment compatible with current mutation locking and source ownership?
• Does the Add column entry remain a thin discovery route into Sources without creating a competing suggestion or relationship workflow?
• Are translated search and the existing From [source] grouping understandable without changing source-field identity or write ownership?

Prospective stack order

This draft is the intended base of a future dependency stack, but this PR does not create or authorize any child branch or PR:

1. PR Connect Add Column to Sources #2662 — Add column → existing Sources UI (this change)
2. Refresh/phantom lane — only after separate evidence, shaping, and Alice authorization
3. 587/589 hydration lane — only after separate evidence, shaping, and Alice authorization
4. Review Diff latency lane — only after separate evidence, shaping, and Alice authorization

Product roadmap impact

content_product_impact:
  lane: local_refinement
  features:
    - content.feature.connect-your-sources
  capabilities:
    - content.source.catalog
    - content.object.database
  record_change: none
  proof:
    - 86 focused Add column, source action, and database UI tests
    - 200 Content database tests
    - full Content suite, Content typecheck, and 50/50 repository guards
    - exact-head independent technical review and H1-H7 real-interface acceptance
  rationale: The change makes existing Source discovery available from Add column without claiming the governed catalog or cross-source Query contract is complete.

[github-actions]

Visual recap — skipped

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Recap skipped for 0c30726: draft PR.