[ENG-1856] Store source identity metadata for Roam imported nodes

[sid597]

What

Adds the Roam-side storage layer for imported cross-app node identity (ENG-1856, M2 "Bidirectional node import"). When Roam imports an Obsidian-origin shared node, it must remember the node's stable source identity so it can (a) prevent duplicate imports and (b) refresh it later.

apps/roam/src/utils/importedSourceIdentity.ts:

• ImportedSourceIdentity — 6 app-neutral fields mirroring the CrossAppNode contract: sourceApp, sourceSpaceId, sourceNodeId, sourceNodeRid, sourceTitle, sourceModifiedAt.
• toImportedSourceIdentity(node) — derive the stored identity from a CrossAppNode (title from the direct content variant).
• writeImportedSourceIdentity(uid, identity) / readImportedSourceIdentity(uid) — persist/read under the page's :block/props → discourse-graph → importedFrom, merging alongside any sibling discourse-graph props (mirrors migrateRelations / createReifiedBlock).
• findImportedNodeUidByRid(rid) — datalog lookup returning an already-imported page's uid (duplicate prevention), keyed on the canonical sourceNodeRid.

Storage is block-props (not page content), so identity survives content overwrite on import/refresh and is datalog-queryable.

Scope / boundaries (pre-flight approved)

This is a foundational helper PR — the exported helpers are the deliverable; their consumers are downstream M2 issues, so there is no in-PR caller by design:

• ENG-1855 marks already-imported nodes via findImportedNodeUidByRid
• ENG-1858 materializer writes identity via writeImportedSourceIdentity(uid, toImportedSourceIdentity(node))
• ENG-1859 import action dedups; ENG-1860 / ENG-1861 refresh read identity + sourceModifiedAt

Deliberately out of scope (named owners): node-type mapping → ENG-1858; author/provenance → ENG-1875; discovery UI → ENG-1855.

Notes for review

• IMPORTED_FROM_PROP_KEY is exported following the existing DISCOURSE_GRAPH_PROP_NAME precedent (wire-key constants exported from their owning module); ENG-1861 (refresh-all) / ENG-1875 (provenance) will enumerate imported pages by it.
• The single as [string][] on the datalog result matches strictQueryForReifiedBlocks's handling of untyped query output.
• Builds on merged ENG-1847 (CrossAppNode + rid.ts); branched off main@36e3348.

Tests

• vitest unit tests for the pure functions — toImportedSourceIdentity and parseImportedSourceIdentity (round-trip + rejection of missing / wrong-typed fields and unknown sourceApp, and coexistence with sibling discourse-graph props): 8/8 pass.
• prettier / eslint / tsc clean on changed files. (Two pre-existing tsc errors in discourseNodeSearchProviders.ts are unrelated to this PR.)

Runtime proof (Loom — owed)

write/read/find call window.roamAlphaAPI; with no UI consumer yet, proof is a console round-trip on a test page PUID:

const id = {sourceApp:"obsidian",sourceSpaceId:"obsidian:vault",sourceNodeId:"abc",sourceNodeRid:"orn:obsidian.note:vault/abc",sourceTitle:"T",sourceModifiedAt:"2026-06-14T10:30:00.000Z"};
await roamAlphaAPI.data.block.update({block:{uid:PUID,props:{"discourse-graph":{importedFrom:id}}}});   // write
roamAlphaAPI.pull("[:block/props]",[":block/uid",PUID]);                                                 // confirm stored
// overwrite the page body here, then re-pull to show identity persists
await roamAlphaAPI.data.async.q(`[:find ?u :in $ ?rid :where [?p :block/uid ?u][?p :block/props ?pr][(get ?pr :discourse-graph) ?d][(get ?d :importedFrom) ?i][(get ?i :sourceNodeRid) ?rid]]`,"orn:obsidian.note:vault/abc"); // find → [[PUID]]; unknown rid → []

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[linear-code]

ENG-1856

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
discourse-graph	Skipped		Jun 26, 2026 3:27pm

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.