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>

bot_bottle/manifest/git.py

@@ -117,7 +117,7 @@ class ManifestGitEntry:
     UpstreamHost: str = ""
     UpstreamPort: str = ""
     UpstreamPath: str = ""
-    # Optional forge alias (PRD prd-new-trusted-agent-forge-identity). When
+    # Optional forge alias (PRD 0082). When
     # set, it must match a `forge-accounts` alias on the selected agent; the
     # composition enables a scoped proxy-held API credential and forge
     # workflow guidance for this repo. Empty = no forge association.
@@ -309,12 +309,12 @@ def parse_git_gate_config(
     raw: object,
 ) -> tuple[ManifestGitEntry, ...]:
     """Parse `git-gate` on a bottle. Only `repos` is accepted; `git-gate.user`
-    moved to the agent's `author` block (PRD prd-new-trusted-agent-forge-identity)."""
+    moved to the agent's `author` block (PRD 0082)."""
     d = as_json_object(raw, f"bottle '{bottle_name}' git-gate")
     if "user" in d:
         raise ManifestError(
             f"bottle '{bottle_name}' git-gate.user is no longer supported "
-            f"(PRD prd-new-trusted-agent-forge-identity). Move name/email into "
+            f"(PRD 0082). Move name/email into "
             f"the selected home agent's 'author' block:\n"
             f"  author:\n    name: <name>\n    email: <email>\n"
             f"Identity is agent-owned; git-gate now carries only transport "