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>

README.md

@@ -16,7 +16,7 @@ enforces anything yet. No platform has a working build.
 | Milestone | State |
 |---|---|
 | M0 repo bootstrap | in progress |
-| M1 core engine | engine, lock timers and safety guarantees written and tested; storage has no I/O yet |
+| M1 core engine | engine, lock timers and safety guarantees written and tested; SQLite persistence landed in `storage/` |
 | M2-Linux | not started — daemon is a placeholder |
 | M3-Android | not started |
 | M4 conditions | not started |
@@ -74,6 +74,7 @@ summary as not-passes. A skip is never reported as a pass.
 
 ```
 core/                 the decision engine — pure, no OS calls, no dependencies
+storage/              SQLite persistence (rusqlite, bundled), fail-open recovery
 tests/                golden decision tables, and the engine purity check
 desktop/daemon/       long-lived observer and enforcer (5 MB budget)
 desktop/ui/           block-screen window, launched on demand
@@ -106,9 +107,10 @@ scripts/              ci.sh, size-check.sh
 | Daemon binary | ≤ 5 MB stripped |
 | APK size | ≤ 10 MB |
 
-Currently measured: **0.279 MB** stripped daemon — a placeholder that prints two
-lines. The meaningful number comes in M2-Linux. Enforced in CI from the first
-commit by `scripts/size-check.sh`.
+Currently measured: **1.364 MB** stripped daemon, which includes bundled SQLite.
+Of the 5 MB budget that leaves 3.8 MB for D-Bus, X11 and a UI toolkit — a real
+margin rather than a comfortable one. Enforced in CI from the first commit by
+`scripts/size-check.sh`.
 
 ## Licence