feat(fleet): generalize topology + 'Go Standalone' mode

CONTEXT.md

@@ -59,9 +59,13 @@ _Avoid_: cron, scheduler (as concept names), night shift
 ### Fleet & serving
 
 **Server mode**:
-The per-machine stance for where Sessions are served from, in three values. `standalone` — this machine spawns and owns its own chat server (the default; the only mode that ever spawns). `server` — this machine runs the Canonical Server as a system service and the panel attaches to it. `client` — this machine never serves; the panel attaches to the Canonical Server through a Managed Tunnel. Machine-scoped, never synced: a synced "client" landing on the server would silence the fleet.
+The per-machine stance for where Sessions are served from, in three values. `standalone` — this machine spawns and owns its own chat server (the default; the only mode that ever spawns). `server` — this machine runs the Canonical Server as a system service and the panel attaches to it. `client` — this machine never serves; the panel attaches to the Canonical Server through a Managed Tunnel. Determined by `~/.amico/ops/fleet/fleet.json` (no file = standalone). Machine-scoped, never synced.
 _Avoid_: profile, spawn vs attach (as concept names)
 
+**Fleet config**:
+The file at `~/.amico/ops/fleet/fleet.json` that declares this machine's fleet role and the canonical server's coordinates (`host`, `port`, `sshAlias`). No file on disk = standalone. The guard script, extension, and installer all resolve role from this file — never from a hardcoded hostname.
+_Avoid_: fleet.toml, fleet settings (those are VS Code settings, a different thing)
+
 **Canonical Server**:
 The one chat server that owns the fleet's Session store — the single writer every panel attaches to. Runs as a system service on the machine in `server` Server mode, available headless (no editor required). Only one may exist per Fleet.
 _Avoid_: master, primary, host
@@ -70,13 +74,9 @@ _Avoid_: master, primary, host
 The user's machines acting as one logical studio: exactly one Canonical Server plus zero-or-more clients, all attaching to the same Session store.
 _Avoid_: mesh, cluster
 
-**Local fallback**:
-The deliberate, user-invoked escape hatch: a `client` machine temporarily serving itself locally (a `standalone` spawn) while the Canonical Server is unreachable. Explicit about its trade-off — fleet history returns on reconnect, and Sessions made during fallback merge back into the Canonical Server on rejoin. Never silent: an active Local fallback is a first-class, visible state.
-_Avoid_: offline mode, degraded mode
-
-**Rejoin**:
-The closing half of Local fallback: on reconnect, the client ships its local Session shard to the Canonical Server, which merges it as the single writer (id-guarded inserts, strictly-newer-wins per row, event-position guard, schema-drift column mapping). After Rejoin, fleet history is whole again — nothing strands on the client.
-_Avoid_: sync (bidirectional connotation), upload
+**Go Standalone**:
+The user-invoked mode switch from `client` to `standalone` — the machine leaves the fleet and serves itself permanently. Not an escape hatch: a first-class choice. Sessions made locally stay local. Re-enrollment in a fleet is a separate flow (Enroll, deferred).
+_Avoid_: local fallback, offline mode, degraded mode
 
 **Fleet token**:
 The shared secret authenticating a client to the Canonical Server's data routes — minted when the fleet server is enabled, stored at 0600, handed to clients during the ssh-based setup flow. The sibling of the per-boot server password (ADR 0002): that guards a spawned server its extension owns; this guards the service no extension spawns.

packages/extension/package.json

@@ -179,16 +179,8 @@
         "title": "Amicode: Fleet — Repair (guard + tunnel)"
       },
       {
-        "command": "amicode.fleet.fallback.enter",
-        "title": "Amicode: Fleet — Enter Local Fallback (work offline)"
-      },
-      {
-        "command": "amicode.fleet.fallback.exit",
-        "title": "Amicode: Fleet — Exit Local Fallback (restore tunnel)"
-      },
-      {
-        "command": "amicode.fleet.rejoin",
-        "title": "Amicode: Fleet — Rejoin (merge fallback sessions)"
+        "command": "amicode.fleet.goStandalone",
+        "title": "Amicode: Fleet — Go Standalone (leave fleet, run locally)"
       },
       {
         "command": "amicode.repo.sync",

packages/extension/scripts/assert_fleet_guard.sh

@@ -12,11 +12,10 @@ ok() { echo "[fleet-gate] ok $*"; }
 
 [[ -f "$GUARD" ]] || fail "guard missing at $GUARD (fleet hardening not merged?)"
 [[ -x "$GUARD" ]] || fail "guard not executable — chmod +x $GUARD"
-grep -q 'Aarons-Mac-mini' "$GUARD" || fail "guard does not mention canonical host Aarons-Mac-mini"
+grep -q 'fleet.json' "$GUARD" || fail "guard does not reference fleet.json config"
 grep -q 'exit 1' "$GUARD" || fail "guard missing client exit 1 (would not prevent fork)"
 grep -q 'FROZEN.*\.amico/server/bin/opencode' "$GUARD" || fail "guard missing frozen binary path"
-grep -q 'FALLBACK.*\.amico/ops/fleet/fallback.json' "$GUARD" || fail "guard missing fallback marker check (CONTEXT.md Local fallback)"
-grep -q 'Local fallback' "$GUARD" || fail "guard missing Local fallback comment/hint"
+grep -q 'FLEET_CONFIG' "$GUARD" || fail "guard missing FLEET_CONFIG variable"
 ok "guard $GUARD"
 
 [[ -f "$INSTALL" ]] || fail "installer missing at $INSTALL"
@@ -32,8 +31,7 @@ ok "tunnel plist $PLIST"
 
 # Guard + tunnel template are the source of truth for the installer; ensure the
 # installer itself is consistent (it references both).
-grep -q "FLEET_GUARD_REL" "$ROOT/packages/extension/src/fleet_health.ts" || fail "fleet_health.ts missing FLEET_GUARD_REL"
-grep -q "FLEET_PORT.*4096" "$ROOT/packages/extension/src/fleet_health.ts" || fail "fleet_health.ts missing FLEET_PORT 4096"
+grep -q "FLEET_GUARD_REL\|FLEET_CONFIG_PATH\|fleet.json" "$ROOT/packages/extension/src/fleet_health.ts" || fail "fleet_health.ts missing fleet config reference"
 
 # Packaged copy must stay in sync with repo root (the VSIX ships the packaged copy).
 PKG_GUARD="$ROOT/packages/extension/tools/fleet/amico-opencode-fleet-guard"