daemon: correct ARCHITECTURE doc to match actual package shape + lock scope

Two promises the doc was making that the code doesn't keep:

1. "Helpers moved out so the package stays focused on orchestration."
   The package still has ~29 files and ~130 func (d *Daemon) methods
   wiring VM lifecycle, image management, host networking, background
   reconciliation, and JSON-RPC dispatch. Calling it "just orchestration"
   sets readers up for surprise. Rewrite the subpackages preamble to
   say so, and flag the service split as a post-v0.1.0 project.

2. "vmLocks[id] is held only across short synchronous state validation
   and DB mutations." That's what workspace.prepare does; regular
   lifecycle ops (start/stop/delete/set) go through withVMLockByRef
   and hold the lock across the whole callback body, which for `start`
   means preflight + bridge + firecracker spawn + post-boot wiring.
   Rewrite the vmLocks bullet and the lock-ordering section to say
   that explicitly, so readers don't build "surely my long flow under
   the lock can't be what the doc means" reasoning on top of a false
   premise.

Doc-only change. Code behaviour is unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/daemon/ARCHITECTURE.md

@@ -10,14 +10,20 @@ primitives, and the lock ordering every caller must respect.
 owning types:
 
 - Layout, config, store, runner, logger, pid — infrastructure handles.
-- `vmLocks vmLockSet` — per-VM `*sync.Mutex`, one per VM ID. Held only
+- `vmLocks vmLockSet` — per-VM `*sync.Mutex`, one per VM ID. Held for
-  across short, synchronous state validation and DB mutations so slow
+  the **entire lifecycle op** on that VM: a `start` holds it across
-  guest I/O does not block lifecycle ops on the same VM.
+  preflight, bridge setup, firecracker spawn, and post-boot wiring
+  (seconds to tens of seconds). Two `start`/`stop`/`delete`/`set` calls
+  against the same VM therefore serialise; calls against different VMs
+  run independently. If you need a slow guest-side operation to NOT
+  block lifecycle ops on the same VM, scope it out of the lock
+  explicitly the way `workspace.prepare` does (see below).
 - `workspaceLocks vmLockSet` — per-VM mutex scoped to
-  `workspace.prepare` / `workspace.export`. Serialises concurrent
+  `workspace.prepare` / `workspace.export`. These ops acquire
-  workspace operations on a single VM (two simultaneous tar imports
+  `vmLocks[id]` only long enough to validate VM state + snapshot the
-  would clobber each other) without touching `vmLocks`, so
+  fields they need, release it, then acquire `workspaceLocks[id]` for
-  `vm stop` / `delete` / `restart` never queue behind a slow import.
+  the slow guest I/O phase. That keeps `vm stop` / `delete` / `restart`
+  from queueing behind a running tar import.
 - `handles *handleCache` — in-memory map of per-VM transient kernel/
   process handles (PID, tap device, loop devices, DM target). The
   cache is rebuildable: each VM directory holds a small
@@ -40,10 +46,18 @@ owning types:
 
 ## Subpackages
 
-Pure helpers have moved into subpackages so the daemon package itself stays
+Stateless helpers that don't need the `Daemon` composition root have
-focused on orchestration. Each subpackage takes explicit dependencies
+been lifted into subpackages. Lifecycle orchestration, image-registry
-(typically a `system.Runner`-compatible interface) and holds no global
+orchestration, host networking bootstrap, background reconciliation,
-state beyond small test seams.
+and the JSON-RPC dispatch all still live in this package — it is not
+"just orchestration." ~29 files and ~130 `func (d *Daemon)` methods
+share the root struct today. A future project would be to split VM
+lifecycle, image management, and the background reconciler into
+services with explicit interfaces; that's out of scope for v0.1.0.
+
+Each subpackage takes explicit dependencies (typically a
+`system.Runner`-compatible interface) and holds no global state beyond
+small test seams.
 
 | Subpackage                        | Purpose                                                                |
 | --------------------------------- | ---------------------------------------------------------------------- |
@@ -67,7 +81,9 @@ vmLocks[id]  →  workspaceLocks[id]  →  {createVMMu, imageOpsMu}  →  subsys
 `vmLocks[id]` and `workspaceLocks[id]` are NEVER held at the same
 time. `workspace.prepare` acquires `vmLocks[id]` just long enough to
 validate VM state, releases it, then acquires `workspaceLocks[id]`
-for the guest I/O phase.
+for the guest I/O phase. Regular lifecycle ops (`start`, `stop`,
+`delete`, `set`) do NOT do this split — they hold `vmLocks[id]`
+across the whole flow.
 
 Subsystem-local locks (`tapPool.mu`, `opstate.Registry` mu) are leaves.
 They do not contend with each other.
@@ -75,7 +91,8 @@ They do not contend with each other.
 Notes:
 
 - `vmLocks[id]` is the outer lock for any operation scoped to a single VM.
-  Acquired via `withVMLockByID` / `withVMLockByRef`.
+  Acquired via `withVMLockByID` / `withVMLockByRef`. The callback runs
+  under the lock — treat the whole function body as critical section.
 - `createVMMu` and `imageOpsMu` are narrow: each guards one family of
   mutations and is released before any blocking guest I/O.
 - Holding a subsystem-local lock while calling into guest SSH is

internal/daemon/doc.go

@@ -67,6 +67,10 @@
 //
 //	vmLocks[id]  →  workspaceLocks[id]  →  {createVMMu, imageOpsMu}  →  subsystem-local locks
 //
-// Subsystem-local locks (tapPool.mu, opstate.Registry mu) are leaves and
+// vmLocks[id] is held across entire lifecycle ops (start/stop/delete/set),
-// do not contend with each other. See ARCHITECTURE.md for details.
+// not just a validation window — callers that want to avoid blocking
+// lifecycle on slow guest I/O must explicitly split off to
+// workspaceLocks[id] the way workspace.prepare does. Subsystem-local
+// locks (tapPool.mu, opstate.Registry mu) are leaves and do not contend
+// with each other. See ARCHITECTURE.md for details.
 package daemon