feat(manifest): trusted agent forge identity and guidance

Implements PRD prd-new-trusted-agent-forge-identity. Moves author identity
and named forge configurations onto the trusted, host-only agent definition,
and lets a bottle repository optionally associate a git-gate repo with one of
the agent's forge aliases.

- Agent-owned identity: new `author` (name/email) and `forge-accounts`
  (alias -> canonical Gitea /api/v1 origin + host `token_secret` ref) on the
  agent manifest. `author` populates the bottle's git user.name/user.email.
- Remove `git-gate.user` from both agents and bottles; fail with a migration
  pointer to `author`. `git-gate` is no longer accepted on an agent.
- Bottle git-gate repos gain optional `forge: <alias>`, resolved against the
  selected agent's forge-accounts at composition (fail-closed on unknown).
- Fail-closed Gitea API URL validation (https, no userinfo/query/fragment,
  /api/v1 base, host lowercased, trailing slash normalized, host dedup).
- Proxy-held credential: synthesize one inspected, token-authenticated egress
  route per referenced forge alias, scoped to the origin + API prefix. The
  token is resolved from the host env at launch into the egress proxy only —
  never the bottle env, prompt, gitconfig, or workspace.
- Generated, non-secret forge workflow guidance appended to the agent prompt
  for associated repos (API base, branch-backed PR flow, AGit-ref prohibition,
  mutation verification); omitted when no repo declares a forge.
- Agents become home-only: cwd `.bot-bottle/agents` no longer contributes,
  overrides, or is selectable; warned-and-ignored like cwd bottles.
- Docs: README examples, PRD 0011 supersession note, manifest schema docstring.
- Tests: new test_forge_identity suite; legacy git-gate.user/cwd tests updated
  to the agent-owned identity model.

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

bot_bottle/manifest/__init__.py

@@ -1,10 +1,10 @@
 """Manifest dataclasses (PRD 0011 layout).
 
-Reads the per-file manifest tree:
+Reads the per-file manifest tree (home-only —
+PRD prd-new-trusted-agent-forge-identity):
 
   $HOME/.bot-bottle/bottles/<name>.md   — one bottle per file
-  $HOME/.bot-bottle/agents/<name>.md    — home-resident agents
-  $CWD/.bot-bottle/agents/<name>.md     — cwd-supplied agents
+  $HOME/.bot-bottle/agents/<name>.md    — agents
 
 Each file is Markdown with YAML frontmatter. The frontmatter holds
 the structured config (see schema below); for agents the body is
@@ -15,27 +15,38 @@ Bottle schema (frontmatter):
   extends:      <bottle-name>                   # optional (PRD 0025)
   env:          { <NAME>: <env-entry>, ... }
   git-gate:                                     # optional (PRD 0047)
-    user:       { name: <str>, email: <str> }   # optional
     repos:      { <name>: <git-gate-entry>, ... }  # optional
+      # git-gate-entry keys: url, key, host_key, forge
+      # `forge`: optional alias into the selected agent's forge-accounts
   egress: { routes: [ <egress-route>, ... ] }
     # route keys: host, matches, auth, role, dlp
   supervise:    <bool>                          # optional (default true)
   nested_containers: <bool>                     # optional (default false)
 
 Agent schema (frontmatter):
-  bottle:        <bottle-name>          # required
+  bottle:        <bottle-name>          # optional
   skills:        [ <skill-name>, ... ]   # optional
-  git-gate:
-    user:        { name: <str>, email: <str> }  # optional; overlays bottle
+  author:                               # optional; agent git identity
+    name:  <str>                        # required when author is present
+    email: <str>                        # required when author is present
+  forge-accounts:                       # optional; alias -> forge account
+    <alias>:
+      url:  <https Gitea /api/v1 base>
+      auth: { type: token, token_secret: <host env var name> }
   # Claude Code subagent passthrough fields — accepted, ignored:
   name, description, model, color, memory
 
+`author` populates the bottle's git user.name/user.email; `forge-accounts`
+maps a forge alias to a Gitea API origin plus a host token reference. Identity
+is agent-owned — `git-gate` is no longer accepted on an agent (git-gate.user
+moved to `author`; git-gate.repos is bottle-only).
+
 The agent file's Markdown body is the system prompt (stripped).
 Unknown top-level frontmatter keys raise ManifestError with a hint.
 
-Bottles can ONLY live under $HOME. A bottles/ dir under $CWD is a
-warn at load time and contributes nothing. The trust boundary is
-expressed as filesystem layout rather than resolver logic.
+Both bottles and agents can ONLY live under $HOME. An agents/ or bottles/
+dir under $CWD is a warn at load time and contributes nothing. The trust
+boundary is expressed as filesystem layout rather than resolver logic.
 
 Two types are exported:
 
@@ -66,6 +77,11 @@ if TYPE_CHECKING:
     from .agent import ManifestAgent, ManifestAgentProvider
     from .bottle import ManifestBottle
     from .egress import EGRESS_AUTH_SCHEMES, ManifestEgressConfig, ManifestEgressRoute
+    from .forge import (
+        ManifestAuthor,
+        ManifestForgeAccount,
+        ResolvedForgeAssociation,
+    )
     from .git import ManifestGitEntry, ManifestGitUser, ManifestKeyConfig
 
 
@@ -81,6 +97,9 @@ _LAZY_MODULES: dict[str, str] = {
     "EGRESS_AUTH_SCHEMES": "egress",
     "ManifestEgressRoute": "egress",
     "ManifestEgressConfig": "egress",
+    "ManifestAuthor": "forge",
+    "ManifestForgeAccount": "forge",
+    "ResolvedForgeAssociation": "forge",
     "ManifestGitEntry": "git",
     "ManifestGitUser": "git",
     "ManifestKeyConfig": "git",
@@ -115,4 +134,7 @@ __all__ = [
     "EGRESS_AUTH_SCHEMES",
     "ManifestEgressRoute",
     "ManifestEgressConfig",
+    "ManifestAuthor",
+    "ManifestForgeAccount",
+    "ResolvedForgeAssociation",
 ]