feat: MCP-Leseserver, Bibliotheksgrenze, Haertung des Lesepfads, Publish-Remote-Gate scharf (2.4.0)

Files changed:
- .gitea/workflows/ci.yml
- CHANGES.md
- README.md
- VERSION
- instructions/mcp-read-server.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/api.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/lint.py
- tools/chemenu/commands/search.py
- tools/chemenu/commands/types_cmd.py
- tools/chemenu/config.py
- tools/chemenu/corpus_cache.py
- tools/chemenu/errors.py
- tools/chemenu/frontmatter_io.py
- tools/chemenu/lint_core.py
- tools/chemenu/mcp/__init__.py
- tools/chemenu/mcp/__main__.py
- tools/chemenu/mcp/server.py
- tools/chemenu/page.py
- tools/chemenu/search/filters.py
- tools/chemenu/search/registry.py
- tools/chemenu/search/ripgrep.py
- tools/chemenu/search/service.py
- tools/chemenu/tests/conftest.py
- tools/chemenu/tests/test_api.py
- tools/chemenu/tests/test_corpus_cache.py
- tools/chemenu/tests/test_doctor.py
- tools/chemenu/tests/test_frontmatter_io.py
- tools/chemenu/tests/test_instructions_cmd.py
- tools/chemenu/tests/test_mcp_server.py
- tools/chemenu/tests/test_new_page.py
- tools/chemenu/tests/test_search.py
- tools/chemenu/type_resolver.py
- tools/chemenu/types_core.py
- tools/requirements-mcp.txt

tools/README.md

@@ -34,20 +34,40 @@ tools/
   wikitool                 entry point
   chemenu/
     cli.py                 Typer app: registers every command, runs the budget gate
-    config.py              repo layout constants (ROOT, RAW_DIR, KB_DIR, WORK_DIR, ...)
+    config.py              repo layout: root resolution and every path under it
+    api.py                 the in-process entry point - point Chemenu at a corpus and read it
+    errors.py              ChemenuError / ValidationError / BackendError
+    corpus_cache.py        one parsed corpus per commit, never cached while the tree is dirty
     kb_scan.py             page iteration/loading over kb/
     kb_collections.py      collection discovery (a directory with COLLECTION.md)
     type_resolver.py       type-spec loading and schema resolution
+    lint_core.py           the lint checks and the report, with no CLI attached
+    types_core.py          type-spec listing/description, with no CLI attached
     sections.py            the section headings the tool reads and writes in a page body
     markdown_code.py       masks code spans/fences so a page may show wiki notation, not only use it
     version.py             the stack version: VERSION, the release stamp, the compatibility rule
     kb_state.py            the KB version (.wikitool-kb.json) and the migration chain
     corpus_diff.py         invariant comparison of kb/ between two revisions
-    search/                pluggable search backends (base protocol, ripgrep, filters, fuse)
-    commands/              one module per command or command group
+    search/                pluggable search backends, plus service.py - the search core
+    commands/              one module per command or command group: the terminal adapters
     tests/                 pytest suite
 ```
 
+**Two consumers, one core.** The CLI is not the only caller any more. The cores
+(`search/service.py`, `lint_core.py`, `types_core.py`) hold what decides an
+answer and import no `typer` and no `rich`; the modules under `commands/` turn
+those values into terminal output and those exceptions into exit codes.
+`api.Corpus` is the in-process entry point over the same functions - it takes a
+corpus root, returns exactly the structures the `--json` forms print, and
+raises instead of exiting. A second consumer is therefore a second adapter
+rather than a second implementation, and the write commands are unreachable
+from `api` because nothing under `commands/` is imported there.
+
+**Which corpus.** The root resolves by precedence: an explicit argument, then
+`$CHEMENU_ROOT`, then a walk up from the package's own location. The walk-up is
+the default, so the CLI is unaffected by any of this. Nothing under the root is
+bound at import time - `KB_DIR` and friends follow whatever `ROOT` currently is.
+
 ## Adding a command
 
 1. Write the module under `chemenu/commands/`. A group is a `typer.Typer()`