Closes Phase 4b by exposing the TTL sidecar written by
Phase 4b primitives on the wire and via `claw-cargo pin`.
Wire additions:
* Method::SetTagExpiry (0x1a) — payload `key_len:u16 || key ||
expires_at:u64 (LE)`. Reply single-byte OK. `expires_at == 0`
clears the sidecar.
* Method::GetTagExpiry (0x1b) — payload raw key bytes. Reply 8
bytes (u64 LE) on hit; NotFound when no sidecar is present.
Both accept writes even when the stamped tag itself is absent,
matching `TagStore::set_stamped_expiry` semantics — the sidecar
takes effect the moment the tag lands.
CLI:
* `claw-cargo pin --ttl <duration>` — humantime-style duration
(`30d`, `1h30m`, `2w`, ...). Applied to both the primary tag
and its `.fingerprint` companion so eviction treats them as
one lifetime. `--ttl 0` / `clear` / `none` clears an existing
sidecar without touching the value.
Tests: encode/decode roundtrip + malformed-input rejection for
`encode_expiry_record`, method-byte stability, NotConfigured
without a tag store, end-to-end set/get/overwrite/clear over
QUIC, and a real-pin flow that publishes a stamped tag then
attaches TTL. Duration parser is unit-tested for single/compound
forms, case-insensitive units, bad input, and clock alignment.
No new deps — the humantime-style parser is 60 lines in-tree.
Co-Authored-By: Claude Opus 4.7 <[email protected]>
