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.

AGENTS.md

@@ -13,6 +13,18 @@ messages. Scope and non-scope are in [README.md](README.md).
 There is no central server, no owner, no registration and no majority vote.
 Design accordingly: a majority is not a root of trust.
 
+## User experience
+
+User convenience is a core requirement. The CLI should feel logical and
+predictable to an experienced administrator: use consistent selectors and
+flags, sensible defaults, and actionable errors. Let users refer to configured
+networks by their exact name as well as by id or a unique id prefix; do not
+make them copy an opaque identifier when the stored name identifies one network.
+When a selector is ambiguous, list the matching names and ids and change
+nothing. Never guess which resource a destructive command should affect.
+Keep help text and examples in sync with behavior, and preserve existing
+scripts when improving the interactive workflow.
+
 ## Architectural boundaries
 
 Keep these separate. Crossing them is the main thing to review for.