Instrument and improve incremental workspace checks

Profile source capture, Nix evaluation/realization, resource/query checking,
and implementation builds without putting timings into immutable outputs.
Keep modular repositories; bound independent capture work, snapshot jj once
per observation, and retain final concurrent-edit and Git completeness checks.

Compose exact resource/closure/frontend/toolchain checks as memoized Nix
derivations. Preserve whole-workspace validation and the full compiler path
when no checked dependency is supplied. Share canonical Nixpkgs by content,
index workspace build contexts once, and narrow lock/driver/compiler inputs
with conservative complete-source fallback. Batch React witness checks only
when distinct source closures cannot share ambient declarations; otherwise
run the original independent TypeScript checks.

Seed local authoring toolchains with exact canonical fetch identities when
they match the selected inputs; retain store-path inputs for overrides.
Add generic correctness checks rather than permanent Reader timing/content
fixtures. Verify actual Reader edits and rejection/recovery in a private
workbench, preserving the original user's workbench and runtime.

Query checking currently caches at resource/closure boundaries, not individual
query semantic dependency boundaries. Template helper pins and reproducible
fixture snapshots follow in a separate publication change.

src/capability-language/authoring-check.ts

@@ -64,7 +64,7 @@ export async function checkAuthoring(
     // Repository-scoped agents can check separate immutable candidates in parallel.
     const capture = promisify(callback)("quixos-qx", ["converge", context.workbench, directory], {
       maxBuffer: 4 * 1024 * 1024,
-      env: { ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1", QUIXOS_TRACE_CAPTURE: "1" },
+      env: { ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1", QUIXOS_TRACE_CAPTURE: "1", QUIXOS_TRACE_PROFILE: "1" },
     });
     console.error(`Capture details: ${path.join(output, "capture.log")}`);
     capture.child.stderr?.on("data", (chunk) => appendFileSync(path.join(output, "capture.log"), chunk));
@@ -94,6 +94,9 @@ export async function checkAuthoring(
         resource.kind,
         path.join(output, "nix.log"),
         options.contractOnly,
+        (phase, ms) => {
+          timings[phase] = ms;
+        },
       );
     } finally {
       timings.immutableCheckMs = Math.round(performance.now() - buildStarted);