refactor(tools): bin/{subject}/{method} layout; Go serve+watch modules

Move serve/ (module) -> bin/server, tools/ -> bin/tools, replace bin/kb-watch
bash with bin/watch Go package; self-executing Go shebangs bin/serve.go and
bin/kb/watch.go; Docker + CI + git/import + docs repointed. Multi-stage image
builds static serve+watch binaries (no Go runtime in container).

bin/tools/mdleaves.py

@@ -0,0 +1,84 @@
+import json
+import re
+from pathlib import Path
+
+import mistune
+
+
+def extract_frontmatter(text: str) -> tuple[dict, str]:
+    """Return (frontmatter dict, body). Accepts leading --- yaml ---."""
+    if not text.startswith("---"):
+        return {}, text
+    end = text.find("\n---", 3)
+    if end == -1:
+        return {}, text
+    fm = text[3:end].strip()
+    body = text[end + 4 :]
+    meta: dict = {}
+    for line in fm.splitlines():
+        if ":" in line:
+            key, _, value = line.partition(":")
+            meta[key.strip()] = value.strip().strip("\"'")
+    return meta, body
+
+
+def split_leafs(meta: dict, body: str) -> list[dict]:
+    """Split a markdown body into leaf chunks on H2 (##) boundaries.
+
+    Each leaf keeps the document-level frontmatter (type, related) and gets
+    its own heading + text. H1 is treated as document title, prepended to the
+    first chunk.
+    """
+    title = ""
+    lines = body.splitlines()
+    headers: list[tuple[str, int]] = []
+    for i, line in enumerate(lines):
+        if re.match(r"^# \S", line):
+            title = line.lstrip("#").strip()
+        elif re.match(r"^## \S", line):
+            headers.append((line.lstrip("##").strip(), i))
+    if not headers:
+        text = "\n".join(l for l in lines if l.strip())
+        return [{"heading": title, "text": text.strip()}]
+
+    leafs: list[dict] = []
+    for idx, (heading, start) in enumerate(headers):
+        end = headers[idx + 1][1] if idx + 1 < len(headers) else len(lines)
+        chunk = "\n".join(l for l in lines[start:end] if l.strip())
+        text = chunk
+        if idx == 0 and title:
+            text = f"{title}\n\n{chunk}"
+        leafs.append({"heading": heading, "text": text.strip()})
+    return leafs
+
+
+def to_all(text: str, path: str | Path, repo: str = "") -> list[dict]:
+    meta, body = extract_frontmatter(text)
+    meta.setdefault("type", "reference")
+    meta.setdefault("status", "current")
+    path = str(path)
+    leafs = split_leafs(meta, body)
+    out = []
+    for lf in leafs:
+        out.append({
+            "source": path,
+            "repo": repo,
+            "heading": lf["heading"],
+            "text": lf["text"],
+            "type": meta.get("type", "reference"),
+            "status": meta.get("status", "current"),
+            "related": meta.get("related", ""),
+        })
+    return out
+
+
+def read_markdown(path: Path) -> str:
+    return path.read_text(encoding="utf-8", errors="replace")
+
+
+def walk_markdown(root: Path) -> list[Path]:
+    return sorted(p for p in root.rglob("*") if p.suffix.lower() in (".md", ".markdown"))
+
+
+def leaves_to_json(leaves: list[dict]) -> str:
+    return json.dumps(leaves, ensure_ascii=False, indent=2)