Iteration 2: per-command write-through to project.yaml, CSVs, history.log

Every successful user command now persists through to YAML, the
affected CSVs, and history.log inside the same SQLite transaction,
with the commit-db-last ordering from ADR-0015 §6: validate ->
mutate -> stage text + fsync -> atomic rename -> append history ->
commit. A failure in any text-write step rolls back the SQLite tx,
so disk state is unchanged on failure. Persistence failures are
routed through a new AppEvent::PersistenceFatal which sets a
fatal_message on the App, emits Action::Quit, and is printed to
stderr after terminal teardown so the banner remains above the
shell prompt (ADR-0015 §8).

New persistence module owns the file formats: hand-rolled YAML
schema writer, per-type CSV encoder (RFC 4180, NULL distinct from
empty string, base64 blobs), append-only history.log with ISO-8601
timestamps and successful-only entries. Atomic per-file writes via
tmp + fsync + rename.

The db worker holds an Option<Persistence>; tests still use
Database::open(":memory:") with no persistence. Action::ExecuteDsl
gains a source field carrying the user-typed text, threaded
through to history.log.

Tests: 289 passing (256 lib + 7 new integration + 9 lifecycle + 17
walking-skeleton), 0 failing, 0 skipped. Clippy clean with nursery
lints.

Cargo.lock

@@ -263,6 +263,27 @@ dependencies = [
  "phf",
 ]
 
+[[package]]
+name = "csv"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "52cd9d68cf7efc6ddfaaee42e7288d3a99d613d4b50f76ce9827ae0c6e14f938"
+dependencies = [
+ "csv-core",
+ "itoa",
+ "ryu",
+ "serde_core",
+]
+
+[[package]]
+name = "csv-core"
+version = "0.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "704a3c26996a80471189265814dbc2c257598b96b8a7feae2d31ace646bb9782"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "darling"
 version = "0.23.0"
@@ -1327,8 +1348,10 @@ name = "rdbms-playground"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "base64",
  "chumsky",
  "crossterm",
+ "csv",
  "directories",
  "futures-util",
  "gethostname",