Remove the supervise flag; supervise every bottle

Issue #249: in practice the per-bottle `supervise` flag was never
turned off — all bottles should be supervised. Remove the manifest
flag and make the supervise sidecar unconditional, mirroring egress.

- Reject `supervise:` as a removed bottle key with a migration hint.
- Drop the `supervise` field from ManifestBottle and the extends merge.
- prepare_supervise always returns a SupervisePlan; the plan type is
  now non-optional and the per-backend `is None` guards are gone, so
  the supervise daemon, current-config mount, aliases, and MCP
  registration always render.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YcU7nerbg8cVj9R4EkpfLJ

bot_bottle/manifest.py

@@ -19,7 +19,6 @@ Bottle schema (frontmatter):
     repos:      { <name>: <git-gate-entry>, ... }  # optional
   egress: { routes: [ <egress-route>, ... ] }
     # route keys: host, matches, auth, role, dlp
-  supervise:    <bool>                          # optional
 
 Agent schema (frontmatter):
   bottle:        <bottle-name>          # required
@@ -111,13 +110,6 @@ class ManifestBottle:
     # identity without any git-gate.repos upstreams, and vice versa.
     git_user: ManifestGitUser = field(default_factory=ManifestGitUser)
     egress: ManifestEgressConfig = field(default_factory=ManifestEgressConfig)
-    # Opt-in per-bottle stuck-recovery sidecar (PRD 0013). When true,
-    # the launch step brings up a supervise sidecar that exposes MCP
-    # tools to the agent (egress-block, capability-block) plus mounts
-    # the current-config dir read-only into the agent at
-    # /etc/bot-bottle/current-config. False (the default) skips the
-    # sidecar and mount.
-    supervise: bool = False
 
     @classmethod
     def from_dict(cls, name: str, raw: object) -> "ManifestBottle":
@@ -152,6 +144,13 @@ class ManifestBottle:
                 f"removed. Move it under 'git-gate.user'."
             )
 
+        if "supervise" in d:
+            raise ManifestError(
+                f"bottle '{name}' has a 'supervise' field, which has been "
+                f"removed (issue #249). All bottles are now supervised; the "
+                f"flag was always-on in practice. Delete the field."
+            )
+
         unknown = set(d.keys()) - BOTTLE_KEYS
         if unknown:
             allowed = ", ".join(sorted(BOTTLE_KEYS))
@@ -190,16 +189,9 @@ class ManifestBottle:
             else ManifestEgressConfig()
         )
 
-        supervise_raw = d.get("supervise", False)
-        if not isinstance(supervise_raw, bool):
-            raise ManifestError(
-                f"bottle '{name}' supervise must be a boolean "
-                f"(was {type(supervise_raw).__name__})"
-            )
-
         return cls(
             env=env, agent_provider=agent_provider, git=git,
-            git_user=git_user, egress=egress, supervise=supervise_raw,
+            git_user=git_user, egress=egress,
         )