Make workspace authoring converge through immutable Nix candidates

Coordinate registered resource edits bottom-up into retained exact remote sources.
Use one Nix-owned source graph for provisional checking, template publication,
explicit baseline upgrades and host activation; retain independent runtime pins.

Add scoped contract inspection, historical recovery, derived worklists, crash-safe
locks, named dependency adoption and plain-QX structural editing. Repair TODO
ownership and template instantiation, and document the supported agent workflow.

Validated with protocol and command suites, real jj/Nix convergence and cache
checks, TS/React installed-command acceptance, and fresh TODO first-edit acceptance.
No live deployment or public publication performed. Props projection generation
and a one-command rich feature generator remain explicitly outside this delivery.

test/structural-plan.test.ts

@@ -34,4 +34,13 @@ test("structural plans validate the graph, journal originals, and reject stale e
   await fs.writeFile(applied.journalPath, JSON.stringify(journal));
   assert.equal((await resumeStructure(root, applied.id)).phase, "complete");
   await assert.rejects(() => planStructure(root, request), /Duplicate|duplicate/);
+  // Cross-repository edits may temporarily refer to an unfinished provider.
+  const provisional: StructuralRequest = {kind: "workspace", validation: "syntax", files: [{file: "workspace.qx", edits: [
+    {operation: "import", kind: "interface", name: "NotImplementedYet"},
+  ]}]};
+  const draft = await planStructure(root, provisional);
+  assert.equal(draft.validation, "syntax");
+  await applyStructure(draft);
+  assert.match(await fs.readFile(path.join(root, "workspace.qx"), "utf8"), /import interface NotImplementedYet/);
+  await assert.rejects(() => planStructure(root, {...provisional, validation: "resource-graph"}));
 });