fix(#4132): verify durable runtime surface sources (#4182)

* fix(#4132): verify durable runtime surface sources

* chore(#4132): record PR number in changeset

* test(#4132): cover rejected commands source alias

* fix(#4132): reject aliased package fallback

* test(#4132): cover rejected agents source alias

* test(#4132): cover partially aliased marker provider

* fix(#4132): reject partially aliased source providers

* test(#4132): cover routed source identity probes

* fix(#4132): route installed source identity probes

* refactor(#4132): tighten installer source metadata

* test(#4132): cover corpus trust boundary attacks

* fix(#4132): close installed corpus trust gaps

* refactor(#4132): keep installer authority private

* fix(#4132): preserve private installer fallback

* test(#4132): preserve fixture source authority

* fix(#4132): reject overlapping source fallback

* fix(#4132): avoid redundant installed corpus reads

* refactor(#4132): simplify provider resolution

* test(#4132): sync install tree fixtures after rebase

---------

Co-authored-by: Tom Boucher <trekkie@nomorestars.com>

tests/capability-cli.test.cjs

@@ -1145,6 +1145,10 @@ describe('issue-2322: capability set --runtime materializes an installed third-p
 
     // Step 3 of the issue repro: capability set my-thing --runtime claude --scope global
     const rcd = tmpDir('cap-cli-rcd-');
+    // A global materialization needs one complete Runtime Surface provider.
+    // This fixture exercises the supported legacy compatibility-marker path;
+    // source-less global trees now fail closed and must be upgraded first.
+    fs.writeFileSync(path.join(rcd, '.gsd-source'), path.join(__dirname, '..', 'commands', 'gsd') + '\n');
     const setResult = runGsdTools(
       ['capability', 'set', 'my-thing', '--runtime', 'claude', '--scope', 'global', '--config-dir', rcd, '--raw'],
       cwd,