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/git-resolver.test.ts

@@ -0,0 +1,37 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { mkdtemp, mkdir, writeFile, rm } from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { execFile as callback } from "node:child_process";
+import { promisify } from "node:util";
+import { createGitCapabilityResolver } from "../src/capability-language/git-resolver.js";
+
+const execFile = promisify(callback);
+test("dependency resolution is reusable across processes, concurrent and rejects modified checkouts", async context => {
+  const temporary = await mkdtemp(path.join(os.tmpdir(), "qx-resolver-test-"));
+  context.after(() => rm(temporary, { recursive: true, force: true }));
+  const origin = path.join(temporary, "origin");
+  await mkdir(origin);
+  const git = (...args: string[]) => execFile("git", ["-C", origin, ...args]);
+  await git("init");
+  await writeFile(path.join(origin, "interface.qx"), "contract");
+  await git("add", ".");
+  await git("-c", "user.name=Test", "-c", "user.email=test@example.test", "commit", "-m", "contract");
+  const commit = (await git("rev-parse", "HEAD")).stdout.trim();
+  await git("tag", `quixos-reachability/${commit}`);
+  const source = { resolver: "git" as const, repository: origin, commit };
+  const options = { checkoutRoot: path.join(temporary, "cache") };
+  const a = await createGitCapabilityResolver(options);
+  const b = await createGitCapabilityResolver(options);
+  const [first, second] = await Promise.all([a(source, "interface"), b(source, "interface")]);
+  assert.equal(first.directory, second.directory);
+  const c = await createGitCapabilityResolver(options);
+  assert.equal((await c(source, "interface")).directory, first.directory);
+  await writeFile(path.join(first.directory, "interface.qx"), "changed");
+  const d = await createGitCapabilityResolver(options);
+  await assert.rejects(d(source, "interface"), /modified/);
+  // A failed request is not memoized forever; repair can be observed on retry.
+  await writeFile(path.join(first.directory, "interface.qx"), "contract");
+  assert.equal((await d(source, "interface")).directory, first.directory);
+});