docs(6210): acceptance sweep — src, scripts and frontend leftovers described in the present tense

The acceptance greps found what the per-area passes missed:

- src/scribe: "Phase 7/8" removal notes in projects, settings and
  user_profile; a paragraph promising an auto-summary side effect that no
  longer exists; user_profile's claim that "upcoming MCP profile tools" read
  the profile, which nothing does; an instance count and instance rule
  titles in plugin_context; "MILESTONE 323 DECIDED" in rulebooks.
- scripts/: check_plugin's header and inline comments were a history of
  the incidents behind each guard, with issue numbers in two failure
  messages; check_dangling_styles named this app's classes as its examples;
  check_design_tokens, measure_duplication and mint_plugin_version cited
  issues and checklists.
- frontend/src: forty-odd comments with four-digit issue numbers that the
  earlier frontend scan filtered out as hex colours, plus "used to" and
  "Phase N" notes.

Kept: illustrative ids (`#4181` as a bare-id example, `PR #198`), migration
Create Date headers and one migration's dated data floor, and the plugin
skills' worked examples of how to cite a record.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/check_design_tokens.py

@@ -1,19 +1,18 @@
 #!/usr/bin/env python3
 """Check the frontend's CSS against the tokens its stylesheet declares.
 
-The gap this closes: `services/design_stylesheet.check_code_against_tokens` has
-always been able to answer "does this code use the sheet correctly?", but the
-only thing ever fed to it was recorded SNIPPETS. The app's own components — where
-sixteen unresolvable references were found living quietly (#2319) — were checked
-by nothing at all.
+`services/design_stylesheet.check_code_against_tokens` answers "does this code
+use the sheet correctly?", but inside the app it is fed only recorded SNIPPETS.
+The app's own components, where unresolvable references live quietly, need a
+check of their own.
 
-That was structural rather than an oversight. The drift panel runs in the browser
-and cannot read source files, and the server has no repo access. CI is the only
-place holding both the component sources and the ability to run the check, and it
-only became cheap once `theme.css` became a generated artifact — so the source of
-truth is a local file, with no network and no credentials.
+That is structural. The drift panel runs in the browser and cannot read source
+files, and the server has no repo access. CI is the only place holding both the
+component sources and the ability to run the check, and `theme.css` is a
+generated artifact — so the source of truth is a local file, with no network
+and no credentials.
 
-INSTANCE-AGNOSTIC ON PURPOSE (rule #115). Nothing here knows what a token should
+INSTANCE-AGNOSTIC ON PURPOSE. Nothing here knows what a token should
 be called or which literals are discouraged. Both come from the stylesheet: the
 declarations, and the `SUPERSEDES` block the generator emits. Point it at a
 different install's sheet and it checks that install's rules.