Add the host-side std `tines-store` crate implementing the `tines_core::Store`
trait over a durable, append-only single-file log so a robot's memory survives
reboot.
- Log format: length-prefixed `[u32 LE][postcard]` records (Obs/Trim/Meta).
- On load the index is rebuilt by replaying the log, then every age is
rebased to load time: elapsed time since the last persisted clock marker is
folded into `age_ms` and `stored_at` reset to load `now`, so ages continue
instead of freezing across a reboot.
- Persisted state: released-id set, `next_seq`, and a clock marker in a `Meta`
record; dedupe to the oldest Obs and let the last event per id win so a
re-inserted id survives a trim.
- Implements `next_seq` and `flush`; `trim` writes Trim records best-effort.
- Registered as a workspace member; std-only, `#![forbid(unsafe_code)]`.
- Adds persistence tests (append durability, rebase-on-load, released/seq
persistence). Full gate (fmt, clippy, docs, tests, no_std thumb build) is green.
