docs: record the measured storage cost and the new crate boundary

Updates the ADR log, architecture, limitations, perf table and README to match
what now exists, rather than what was expected.

**The perf number was wrong and is now honest.** The M0 figure of 0.279 MB
excluded SQLite entirely — the placeholder binary never referenced the crate, so
dead-code elimination dropped it. With the daemon actually opening a database it
is **1.364 MB**, of which bundled SQLite is ~1.1 MB. That is 1.1 MB of the 5 MB
budget spoken for, leaving 3.8 MB for D-Bus, X11 and a UI toolkit.

This is the first number that makes the section 5 budget feel like a budget
rather than a formality, and it turns ADR-4's bundled-vs-system-linked choice
into a real trade-off with a measured price on both sides.

- ADR-4 marked accepted and implemented, with that trade-off left open.
- ARCHITECTURE.md documents why `blocker-storage` is a sibling crate and not a
  submodule: the dependency direction is what keeps the zero-dependency purity
  proof automatic rather than a grep someone can route around.
- LIMITATIONS.md drops the stale "storage has no I/O" shortfall and records the
  bundled-vs-system question instead, plus the fact that `LockState` still always
  evaluates to Normal.
- README status table and layout updated.

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

docs/LIMITATIONS.md

@@ -177,9 +177,9 @@ not mistaken for platform facts.
 - **`ProcessBackend` is not implemented.** ADR-14 lists three backends; the KWin
   and X11 paths land in M2-Linux, and the process fallback is weaker than the
   spec assumes because of the `/proc/connectors` gap above.
-- **`rusqlite` has not been added.** The schema is written and reviewed in
-  `core/src/storage.rs` (ADR-4) but storage has no I/O behind it yet, so nothing
-  persists. A restart loses all state.
+- **`rusqlite` vs system-linked SQLite is unresolved** (ADR-4). Bundled is built
+  and costs ~1.1 MB of the 5 MB daemon budget. System-linking would reclaim most
+  of that but adds a runtime dependency on the host's libsqlite3.
 - **Lock state is not yet persisted or enforced.** `core/src/lock.rs` has the
   timers, the escalation, and the wall-clock correction, all tested. The state
   machine is not yet driven from a UI, and `LockState::evaluate` currently returns
@@ -188,6 +188,8 @@ not mistaken for platform facts.
   `tests/src/golden.rs`; parsing needs serde, which is a dependency decision
   awaiting sign-off (ADR-13, ADR-16). The behavioural coverage that exists today
   is hand-written unit tests in the same spirit.
+- **`LockState` still always evaluates to `Normal`** — persistence works, but no
+  UI drives the lock state machine yet.
 - **`Condition::UsageLimit` and `LaunchCount` sum across all targets** rather
   than the schedule's own target set, until targets carry usage keys.
 - **Windows is entirely unimplemented** and cannot be compiled or tested on the