feat(cli): local-state inspection subcommands (status / history / verify) (#13)

Add three read-only `driven-cli` subcommands that inspect the on-disk
state database directly via driven-core's StateRepo, with no Drive or
network access:

- `status`  - each backup source with its file_state counts by status,
  pending-op count, and last scan / deep-verify times.
- `history` - the most recent activity-log entries (--limit, and
  --errors-only to show warnings + errors).
- `verify`  - flags file_state rows in a corrupt / error state and exits
  non-zero when any are found, so it is scriptable.

Each command splits a pure `gather_*` query from the `run_*` renderer so
the query logic is unit-tested against a seeded temporary database. A
dependency-free epoch-ms -> ISO-8601 formatter (Hinnant's civil_from_days)
keeps the timestamps readable without pulling in chrono. A missing --db
path is a clean error rather than silently creating an empty database.


Claude-Session: https://claude.ai/code/session_01WvXMHHbYGddVPpmQR2XmK1

Co-authored-by: Claude <noreply@anthropic.com>

Author: pmaxhogan

Cargo.lock

@@ -23,3 +23,6 @@ anyhow.workspace = true
 tracing.workspace = true
 tracing-subscriber.workspace = true
 clap.workspace = true
+
+[dev-dependencies]
+tempfile = "3"