Remove mikado frontmatter from closed chains, clarify finalization rules

During finalization, all mikado frontmatter (requires, status, branch) should
be removed — cards become plain documentation linked via wiki-links. Updated
agent-change-process docs and cleaned up 10 cards from closed chains. Also
fixed ai-docs referencing deleted plans/ files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

mise-tasks/ai-docs

@@ -13,8 +13,6 @@ FILES=(
     "$DOCS_DIR/reference/reference.md"
     "$DOCS_DIR/how-to/how-to.md"
     "$DOCS_DIR/how-to/operations/troubleshooting.md"
-    "$DOCS_DIR/how-to/plans/plans.md"
-    "$DOCS_DIR/how-to/plans/completed/completed.md"
     "$DOCS_DIR/explanation/explanation.md"
     "$DOCS_DIR/explanation/architecture.md"
     "$DOCS_DIR/tutorials/tutorials.md"

mise-tasks/mikado-branch-invariant-check

@@ -107,7 +107,7 @@ def is_mikado_card(content: str) -> bool:
     """Check if file content has Mikado card frontmatter.
 
     A file is a Mikado card if its YAML frontmatter contains any of:
-    - requires: (dependency list, kept permanently on cards)
+    - requires: (dependency list for active chain cards)
     - status: (e.g. 'active' for in-progress cards)
     - branch: mikado/... (goal cards linking to their branch)
     """