docs: propagate rutster-trunk rename + repo URL through plans/specs/DEVELOPMENT

Mechanical propagation of the crate rename ( rutster-signaling-sip →
rutster-trunk ) and the repo URL fix ( github.com/anomalyco →
git.adlee.work/alee ) through the documents that name them:

- docs/DEVELOPMENT.md: crate-layout sketch + stub-crate description.
- docs/superpowers/plans/2026-06-28-slice-1-webrtc-loopback.md: the
  workspace members list in the plan's binding-values section —
  repository URL updated.
- docs/superpowers/plans/2026-06-28-slice-2-agent-tap.md: workspace
  members list in binding-values + crate-layout sketch in the file-
  structure section (rutster-signaling-sip → rutster-trunk).
- docs/superpowers/specs/2026-06-28-slice-2-agent-tap-design.md: §2.1
  workspace-layout sketch's STUB crate-row.

No content changes beyond the substitutions; the slice-2 spec/plan
body (protocol, TapAudioPipe, TapClient, TapEngine, lifecycle, done-
  criteria) is untouched.

docs/DEVELOPMENT.md

@@ -34,13 +34,13 @@ rutster/
 │   │   ├── src/rtc_session.rs    # RtcSession (per-peer owner)
 │   │   └── src/loop_driver.rs    # str0m poll loop
 │   ├── rutster-call-model/    # the Channel/Leg object embryo
-│   ├── rutster-signaling-sip/ # stub until spearhead step 5
+│   ├── rutster-trunk/ # stub until spearhead step 5
 │   ├── rutster-tap/           # stub until spearhead step 2
 │   └── rutster-spend/         # stub until spearhead step 6
 └── fuzz/                      # placeholder cargo-fuzz dir (real harnesses: step 5)
 ```
 
-The three stub crates (`rutster-signaling-sip`, `rutster-tap`,
+The three stub crates (`rutster-trunk`, `rutster-tap`,
 `rutster-spend`) exist to lock the ADR-0002 boundary shape without
 anticipating code. Each is a `lib.rs` with a `//!` module doc comment
 describing what will land there and when. Don't fill them in early —