docs(prd): assign PRD number 0082

CI (prd-number-check) rejects unnumbered prd-new-*.md on merge to main.
Rename docs/prds/prd-new-trusted-agent-forge-identity.md to
0082-trusted-agent-forge-identity.md (0081 is claimed by #517/#519) and
update the in-repo 'PRD prd-new-trusted-agent-forge-identity' citations to
'PRD 0082'.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_manifest_lazy_loader.py

@@ -72,7 +72,7 @@ class _LazyCase(unittest.TestCase):
 
 class TestAllAgentNamesLazy(_LazyCase):
     def test_cwd_agents_ignored_home_only(self) -> None:
-        # Agents are home-only (PRD prd-new-trusted-agent-forge-identity):
+        # Agents are home-only (PRD 0082):
         # a cwd agents/ dir is warned-and-ignored, so only the home agent
         # appears in all_agent_names.
         _write(self.home_cb / "bottles" / "dev.md", _BOTTLE_DEV)
@@ -100,7 +100,7 @@ class TestRequireAgentLazy(_LazyCase):
         self.resolve().require_agent("alpha")  # no raise
 
     def test_cwd_only_agent_not_selectable(self) -> None:
-        # Agents are home-only (PRD prd-new-trusted-agent-forge-identity):
+        # Agents are home-only (PRD 0082):
         # a cwd-only agent file is never selectable, so require_agent raises.
         _write(self.home_cb / "agents" / "alpha.md", _AGENT)
         _write(self.cwd_cb / "agents" / "beta.md", _AGENT)