Allow network commands to select stored names

Leaving a configured network required copying its opaque id even when its
name identified exactly one saved network. Resolve exact, case-sensitive
names from the existing local state alongside full ids and unique id prefixes.
Use the shared resolver for leave, stop, start, secret and broadcast so the
same selector has the same meaning throughout the CLI. IPC and storage still
operate on the resolved id; release and offline-removal behavior are unchanged.

Refuse ambiguous names and name/id-prefix collisions before any mutation,
listing matching names and full ids without secrets. Full ids take precedence
to provide a definitive escape from ambiguity. Preserve copied id ellipses
without stripping literal ellipses from network names.

Update help and examples. Make administrator-friendly, predictable CLI behavior
a core requirement in AGENTS.md, including actionable errors and no guessing
which resource a destructive command should affect.

Validation on Windows: cargo fmt --all -- --check and workspace/all-target
Clippy with -D warnings passed. Release workspace/all-target tests: 318 passed,
including real-process online/offline leave-by-name, preservation of other
networks, ambiguous/unknown selectors, and consistent name selection across
commands. Two existing Windows SQLite wipe failures were explicitly skipped
(a_wipe_removes_everything_and_the_next_start_is_a_stranger and
wiping_twice_is_as_ordinary_as_wiping_once). The public-DHT smoke test and
forwarding benchmark remain ignored by default. Tests use isolated state;
the user's running agent and configured networks were not changed.

docs/broadcast.md

@@ -8,14 +8,16 @@ control session. It is not a network-wide vote or signed shared configuration.
 ```sh
 tsunagi join -n games --no-broadcast
 tsunagi join -n games --broadcast
-tsunagi network broadcast <network-id-or-prefix> off
-tsunagi network broadcast <network-id-or-prefix> on
-tsunagi network broadcast <network-id-or-prefix>
+tsunagi network broadcast games off
+tsunagi network broadcast games on
+tsunagi network broadcast games
 ```
 
 Joining without either flag preserves the saved choice. The `network broadcast`
 command can change a running network immediately or configure it while the
-agent is stopped. `status` reports the local setting. There is no global `up`
+agent is stopped. It accepts the exact network name, full id or a unique id
+prefix; ambiguous selectors list candidates without changing anything.
+`status` reports the local setting. There is no global `up`
 override: starting the agent preserves every network's independent policy.
 
 ## Delivery

docs/testing.md

@@ -108,6 +108,11 @@ with no secret invents one, prints it in full and prints a line the other
 side can paste unchanged; a bare name this device already knows resumes
 that network instead of inventing another of the same name; and a network
 can be stopped and started again with its secret and its place intact.
+Network selection accepts exact names consistently across commands. Leave-by-name
+is tested with a live agent and with offline state, preserving other networks;
+duplicate and unknown names change nothing and full ids resolve ambiguity.
+Selector unit tests cover case-sensitive names, Unicode/ellipsis names, copied
+id prefixes and collisions between names and ids without revealing secrets.
 
 `crates/tsunagi-cli/tests/dns_service.rs` runs the real binary: the resolver
 comes up with no interface to attach it to, the listener is not rebuilt on