docs: align historical plans/specs with renamed identifiers (roundTrip -> execute, log schema)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/superpowers/specs/2026-07-26-structured-json-logging-design.md

@@ -100,7 +100,7 @@ preflights:
 
 ### Garmin wrapper call log (`internal/garmin`)
 
-`client.go`'s `roundTrip` is the single funnel point every one of the six
+`client.go`'s `execute` is the single funnel point every one of the six
 `Client` methods already goes through (confirmed while surveying: none of
 them ever put Garmin credentials in the wire `params` -- email/password
 only ever reach the subprocess via env vars at spawn time, so logging
@@ -134,7 +134,7 @@ what keeps this safe for the huge per-second-telemetry responses
 while still showing tiny auth results (`{"status":"mfa_required",...}`) in
 full -- exactly the detail needed for the motivating incident.
 
-All six `Client` methods pass their own `ctx` through to `roundTrip`
+All six `Client` methods pass their own `ctx` through to `execute`
 (currently they call it without one). `ensureStarted` also gains a `ctx
 context.Context` param and logs one `Info` line on actual spawn
 (`python_path`, whether a token store is configured) -- spawning the
@@ -163,7 +163,7 @@ subprocess is itself a call to the external component.
   `applog.WithLogger`, call `Authenticate`/`CompleteMFA`, assert the emitted
   JSON line's `cmd`/`duration_ms`/`result_preview` fields, and that a
   wrapper-reported error surfaces at `Warn` with an `error` field. Update
-  the three existing tests that call `roundTrip` directly
+  the three existing tests that call `execute` directly
   (`TestSubprocessClient_RoundTrip_DetectsIDMismatch`,
   `_SubprocessClosedIsError`, `_WrapperErrorPropagates`) to pass
   `context.Background()` as the new first argument.