chore(voyage): release v5.0.1 — drop standalone HTML render; print literal /playground document-critique invocation

The v5.0.0 stop-gap had /trekbrief, /trekplan, and /trekreview each render
a read-only {artifact}.html (via scripts/render-artifact.mjs) AND print a
vague "run the /playground plugin" instruction. In practice the read-only
HTML was redundant with what /playground produces and the instruction
wasn't copy-paste-ready — the operator had to guess the right invocation.

v5.0.1 deletes scripts/render-artifact.mjs + its test + npm run render,
and makes each producing command end with a single boxed, literal,
copy-paste-ready line:

    /playground build a document-critique playground for {artifact_path}

One paste from the operator launches the official playground skill's
document-critique template, which builds an interactive HTML — artifact
on the left, per-line Approve/Reject/Comment cards on the right, Copy
Prompt button at the bottom. Mark suggestions, click Copy Prompt, paste
back, Claude revises the .md. Doc-consistency test pins the literal
invocation so the prose cannot soften back into vagueness.

npm test green: 503 tests, 501 pass, 0 fail, 2 skipped.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plugins/voyage/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "voyage",
-  "description": "Voyage — brief, research, plan, execute, review, continue. Contract-driven Claude Code pipeline; renders produced artifacts to HTML + link, annotate via the /playground plugin.",
-  "version": "5.0.0",
+  "description": "Voyage — brief, research, plan, execute, review, continue. Contract-driven Claude Code pipeline. At the end of /trekbrief, /trekplan, and /trekreview, the operator gets a copy-paste-ready /playground invocation that builds an interactive document-critique HTML for the artifact.",
+  "version": "5.0.1",
   "author": {
     "name": "Kjell Tore Guttormsen"
   },