feat(git-sync): native-Obsidian format — phase 1 = page-file (frontmatter gitmost_id)

Pivot the thin-meta design to "the vault IS a native Obsidian vault": clean
markdown + a minimal YAML frontmatter `gitmost_id:` (the durable pageId, travels
with the file so identity survives any move); folders mirror the page tree with
the parent's body as a folder-note `<Folder>/<Folder>.md` (LostPaul Folder Notes
convention); links as `[[wikilinks]]` (basename-resolved → reparent never breaks a
link, only retitle does); collisions disambiguated Obsidian-style; `.obsidian/`
and non-page files left untouched (no .gitignore). Verified the conventions
against the Obsidian/Folder-Notes docs.

Replaces the abandoned `.gitmost/index.json` sidecar (path-keyed → fragile to
git-undetected renames; the in-file id is self-sufficient): removes vault-index.ts.
Adds lib/page-file.ts — parsePageFile/serializePageFile (frontmatter id + clean
body) with a LEGACY `docmost:meta` fallback for migration. 6 unit tests; engine
suite green. Not yet wired into pull/push — no behavior change. Design doc
rewritten to the native-Obsidian format.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/git-sync/test/page-file.test.ts

@@ -0,0 +1,43 @@
+import { describe, it, expect } from "vitest";
+import { parsePageFile, serializePageFile } from "../src/lib/page-file";
+import { serializeDocmostMarkdownBody } from "../src/lib/index";
+
+describe("page-file thin format", () => {
+  it("round-trips id frontmatter + clean body", () => {
+    const text = serializePageFile("019ef6fc-2638", "# Hello\n\nbody text");
+    expect(text.startsWith("---\ngitmost_id: 019ef6fc-2638\n---\n")).toBe(true);
+    const { id, body } = parsePageFile(text);
+    expect(id).toBe("019ef6fc-2638");
+    expect(body).toBe("# Hello\n\nbody text");
+  });
+
+  it("serialization is deterministic (byte-identical for the same input)", () => {
+    expect(serializePageFile("p", "x")).toBe(serializePageFile("p", "x"));
+  });
+
+  it("reads id from frontmatter with quotes / extra fields", () => {
+    expect(parsePageFile('---\ngitmost_id: "abc"\ntitle: ignored\n---\nbody').id).toBe("abc");
+    expect(parsePageFile("---\ngitmost_id: 'xyz'\n---\nbody").id).toBe("xyz");
+  });
+
+  it("MIGRATION: falls back to a legacy docmost:meta block for the id", () => {
+    const legacy = serializeDocmostMarkdownBody(
+      { version: 1, pageId: "legacy-1", title: "T", spaceId: "sp" },
+      "old body",
+    );
+    const { id, body } = parsePageFile(legacy);
+    expect(id).toBe("legacy-1");
+    expect(body).toContain("old body");
+  });
+
+  it("ADOPT: a plain hand-written file has no id and keeps its whole body", () => {
+    const { id, body } = parsePageFile("# Just a note\n\nwritten in Obsidian");
+    expect(id).toBeNull();
+    expect(body).toBe("# Just a note\n\nwritten in Obsidian");
+  });
+
+  it("tolerates empty / whitespace input", () => {
+    expect(parsePageFile("").id).toBeNull();
+    expect(parsePageFile("   \n  ").body).toBe("");
+  });
+});

packages/git-sync/test/vault-index.test.ts

@@ -1,78 +0,0 @@
-import { describe, it, expect } from "vitest";
-import {
-  emptyVaultIndex,
-  parseVaultIndex,
-  serializeVaultIndex,
-  pageIdAt,
-  slugIdAt,
-  pathForPageId,
-  trackedPageIds,
-  setEntry,
-  removeAt,
-  moveEntry,
-} from "../src/engine/vault-index";
-
-describe("vault-index parse/serialize", () => {
-  it("round-trips a populated index", () => {
-    const idx = emptyVaultIndex("sp1");
-    setEntry(idx, "Проект/index.md", { pageId: "p1", slugId: "Ab12" });
-    setEntry(idx, "Заметка.md", { pageId: "p2" });
-    const text = serializeVaultIndex(idx);
-    const back = parseVaultIndex(text);
-    expect(back.spaceId).toBe("sp1");
-    expect(pageIdAt(back, "Проект/index.md")).toBe("p1");
-    expect(slugIdAt(back, "Проект/index.md")).toBe("Ab12");
-    expect(pageIdAt(back, "Заметка.md")).toBe("p2");
-    expect(slugIdAt(back, "Заметка.md")).toBeUndefined();
-  });
-
-  it("serializes deterministically (sorted keys -> stable diffs)", () => {
-    const a = emptyVaultIndex("s");
-    setEntry(a, "b.md", { pageId: "2" });
-    setEntry(a, "a.md", { pageId: "1" });
-    const b = emptyVaultIndex("s");
-    setEntry(b, "a.md", { pageId: "1" });
-    setEntry(b, "b.md", { pageId: "2" });
-    // insertion order differs; serialized output must be identical.
-    expect(serializeVaultIndex(a)).toBe(serializeVaultIndex(b));
-    // keys are sorted in the output
-    expect(serializeVaultIndex(a).indexOf('"a.md"')).toBeLessThan(
-      serializeVaultIndex(a).indexOf('"b.md"'),
-    );
-  });
-
-  it("is tolerant: null / garbage / bad entries -> empty or skipped", () => {
-    expect(parseVaultIndex(null).pages.size).toBe(0);
-    expect(parseVaultIndex("").pages.size).toBe(0);
-    expect(parseVaultIndex("not json{").pages.size).toBe(0);
-    expect(parseVaultIndex("[1,2,3]").pages.size).toBe(0);
-    // a page entry missing pageId is skipped, valid ones kept
-    const idx = parseVaultIndex(
-      JSON.stringify({ version: 1, pages: { "ok.md": { pageId: "p" }, "bad.md": { slugId: "x" } } }),
-    );
-    expect(idx.pages.size).toBe(1);
-    expect(pageIdAt(idx, "ok.md")).toBe("p");
-  });
-});
-
-describe("vault-index lookups + mutations", () => {
-  it("reverse lookup + tracked set", () => {
-    const idx = emptyVaultIndex();
-    setEntry(idx, "x.md", { pageId: "px" });
-    setEntry(idx, "y/index.md", { pageId: "py" });
-    expect(pathForPageId(idx, "py")).toBe("y/index.md");
-    expect(pathForPageId(idx, "missing")).toBeUndefined();
-    expect([...trackedPageIds(idx)].sort()).toEqual(["px", "py"]);
-  });
-
-  it("moveEntry relocates identity; removeAt drops it", () => {
-    const idx = emptyVaultIndex();
-    setEntry(idx, "Old.md", { pageId: "p", slugId: "s" });
-    moveEntry(idx, "Old.md", "New/index.md");
-    expect(pageIdAt(idx, "Old.md")).toBeUndefined();
-    expect(pageIdAt(idx, "New/index.md")).toBe("p");
-    expect(slugIdAt(idx, "New/index.md")).toBe("s"); // identity preserved
-    removeAt(idx, "New/index.md");
-    expect(pageIdAt(idx, "New/index.md")).toBeUndefined();
-  });
-});