feat(cli): chart resolves a --trace family by its chosen campaign name (#238)

The NotFound arm of emit_chart now queries the recorded campaign runs:
records with a persisted trace_name whose stored campaign document
carries name == ARG. A unique match re-dispatches the existing charting
path onto the resolved handle; several matches refuse listing the
candidate handles in append order (refuse-don't-guess — re-running a
named invocation legitimately yields {campaign8}-0, -1, ...); zero
matches keep the not-found message verbatim. The exact trace-store
handle always wins; the name never becomes a store key (C18 untouched).
Guide §3 and the glossary tap entry document the name alternative.

closes #238

docs/authoring-guide.md

@@ -588,4 +588,7 @@ is non-empty, the run also persists the named taps under
 `runs/traces/<trace_name>/…`, chartable with `aura chart`. The
 `sweep`/`walkforward --trace` analog persists every member's taps as a
 family charted the same way, by the handle the run prints (members keyed
-`<cell>/<member>`).
+`<cell>/<member>`) — also by the `--trace <NAME>` you chose, when that name
+uniquely names one recorded run (`aura chart <NAME>` resolves it against the
+stored campaign documents; a name reused across runs refuses rather than
+guessing which one you mean).