stack: TOC-Pflicht fuer Referenzdateien ueber 100 Zeilen (docs toc); session-setup.md/gates.md nennen die tatsaechliche Budget-Ausnahmeliste (schliesst #73, #76)

Files changed:
- AGENTS.md
- CHANGES.md
- VERSION
- instructions/CONTRACT.md
- instructions/capture-session.md
- instructions/claude-code-model-selection.md
- instructions/dev/issue-tracking.md
- instructions/dev/testing-conventions.md
- instructions/dev/version-parts.md
- instructions/evolve-subtypes.md
- instructions/gates.md
- instructions/german-terminology.md
- instructions/ingest-large-tree.md
- instructions/kb-profiles.md
- instructions/link-taxonomy.md
- instructions/mcp-read-server.md
- instructions/migrate-corpus.md
- instructions/migrations/3.0.0-authoring-conventions.md
- instructions/migrations/4.0.0-link-taxonomy.md
- instructions/private-instance.md
- instructions/session-setup.md
- instructions/setup-instance.md
- kb/CONTRACT.md
- kb/CONVENTIONS.md
- kb/concepts/COLLECTION.md
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/instructions_cmd.py
- tools/chemenu/tests/test_docs_verify.py
- tools/chemenu/tests/test_instructions_cmd.py
- tools/chemenu/tests/test_toc.py
- tools/chemenu/toc.py
- types/type-spec.md

instructions/private-instance.md

@@ -17,6 +17,17 @@ saves the whole update procedure afterwards.
 **Read this before, not after, the first `publish`.** The gate in step 4 is the thing that makes
 the arrangement safe, and adding it later means the window it closes was open in between.
 
+<!-- wikitool:toc -->
+## Contents
+
+- [Why a clone rather than a tarball](#why-a-clone-rather-than-a-tarball)
+- [Steps](#steps)
+- [Taking a stack update](#taking-a-stack-update)
+- [Where stack development happens](#where-stack-development-happens)
+- [Decision points](#decision-points)
+- [Scope](#scope)
+<!-- /wikitool:toc -->
+
 ## Why a clone rather than a tarball
 
 `INSTALL.md`'s "Eine Instanz aktualisieren" is `cp -r` as an upgrade strategy: copy `tools/`,