stack: SKILL.md-Links auf repo-root-relative Pfade umgestellt, docs verify/instructions verify pruefen Linkziele

Files changed:
- CHANGES.md
- VERSION
- instructions/CONTRACT.md
- instructions/dev/doc-pull-through.md
- instructions/dev/stack-close/SKILL.md
- instructions/dev/stack-dev/SKILL.md
- instructions/wiki-ingest/SKILL.md
- instructions/wiki-lint/SKILL.md
- instructions/wiki-manage/SKILL.md
- instructions/wiki-query/SKILL.md
- instructions/wiki-status/SKILL.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

instructions/CONTRACT.md

@@ -18,6 +18,7 @@ alongside [AGENTS.md](../AGENTS.md).
 - [Publishing](#publishing)
 - [Writing an instruction](#writing-an-instruction)
   - [A skill's H1 is a name, not an imperative](#a-skills-h1-is-a-name-not-an-imperative)
+  - [A skill's outbound reference is a plain path, not a link](#a-skills-outbound-reference-is-a-plain-path-not-a-link)
   - [Reference depth: bundled files, not repo-wide contracts](#reference-depth-bundled-files-not-repo-wide-contracts)
   - [When a skill carries a copy-in checklist](#when-a-skill-carries-a-copy-in-checklist)
   - [How much reasoning a step may carry](#how-much-reasoning-a-step-may-carry)
@@ -190,6 +191,35 @@ exception in the same breath - "for promoted skills, the skill name is the title
 That is the whole exception. Everything else in this section binds a `SKILL.md` exactly as it
 binds an instruction.
 
+### A skill's outbound reference is a plain path, not a link
+
+`tools/wikitool instructions sync` copies each `SKILL.md` byte for byte into
+`.agents/skills/<name>/` and `.claude/skills/<name>/` (§ Publishing, above) - a different depth
+than the source, and without the sibling files a relative link might expect. A markdown link
+correct at `instructions/<name>/SKILL.md` (`../session-setup.md`, `../../kb/CONTRACT.md`)
+resolves to a different, usually nonexistent, file once copied: the number of `../` segments
+that reaches a target from `instructions/` does not reach the same target from
+`.claude/skills/`. Fifty-two of the fifty-eight relative links across this repo's seven skills
+broke exactly this way before this rule existed, silently - nothing rendered the copy to notice,
+and no check read a link target.
+
+So a `SKILL.md` never writes an outbound reference as a relative markdown link, correct depth or
+not. It names the target as a repo-root-relative **plain path** instead - `` `instructions/session-setup.md` ``, not `[session-setup.md](../session-setup.md)`; `` `kb/CONTRACT.md` `` for a
+whole file, `` `kb/CONVENTIONS.md` § Tone `` for a section rather than an anchored link. The path
+survives the copy unchanged because it does not depend on where the reading file sits: an
+agent's working directory is the instance root regardless of which published copy it opened, so
+the same plain path resolves in the source and in both published copies alike. The cost is that
+the reference is no longer clickable from the source file - accepted deliberately, because the
+source is not where an agent reads it from; the harness reads the published copy.
+`tools/wikitool instructions verify` enforces the ban mechanically
+(`check_skill_reference_paths`).
+
+This binds only `SKILL.md`. The flat `instructions/<name>.md` form - this file included - is
+never copied anywhere, so its relative links stay exactly as correct as their `../` count says,
+and stay ordinary links; `tools/wikitool docs verify` (`check_reference_targets`) resolves those
+against the working tree instead of banning the syntax, over the same reference-file scope
+`tools/wikitool docs toc` uses.
+
 ### Reference depth: bundled files, not repo-wide contracts
 
 Anthropic's skill-authoring guidance asks that reference files stay **one level deep from
@@ -201,9 +231,11 @@ That rule governs **skill-bundled** material: files sitting in `instructions/<na
 `OOXML.md`), and it says nothing about files outside the skill directory. No skill in this repo
 has a bundled file today, so as written the rule currently binds nothing here.
 
-A link from a skill to a repo-wide contract - [kb/CONTRACT.md](../kb/CONTRACT.md),
-[tools/CONTRACT.md](../tools/CONTRACT.md), [gates.md](gates.md) - is a different category, and
-the two halves of the question have different answers:
+A skill's reference to a repo-wide contract - `kb/CONTRACT.md`, `tools/CONTRACT.md`,
+`instructions/gates.md` (written as a plain path per § "A skill's outbound reference is a plain
+path, not a link" above; this file is a flat instruction rather than a `SKILL.md`, so its own
+references to the same three files, a few sections up and below, stay ordinary links) - is a
+different category, and the two halves of the question have different answers:
 
 - **The mechanic is real and directory-independent.** A contract reached at the second hop can
   be read partially exactly as a bundled file would be. Nothing about the path makes it safe.