Generic markdown importer

Status: shipped in #250 on top of the importer plugin contract from #246.

The generic importer is the catch-all for plain markdown directories that already look like notes — Bear exports, Obsidian vaults, plain folders of .md, dumps from a static-site generator, or anything else that boils down to "a tree of text files I want in my workspace".

It picks up automatically once shipped — the loader scans apps/electron/importers/<id>/ at startup and the entry shows up in the importer chooser modal and the File → Import from… menu.

What it does

When the user picks a folder, the importer:

1. Walks the folder recursively, skipping hidden entries (.git, .obsidian, .DS_Store, etc.) and node_modules.
2. Yields one ImportedNote per file with extension .md, .markdown, or .txt.
3. Preserves the source-folder relative layout via meta.relativePath. The host writes the imported tree out faithfully — folders stay folders, deep paths stay deep.
4. Preserves frontmatter exactly as it appeared in the source file (no rewrite, no normalisation). The host wraps its own bookkeeping fields (created, updated, tags, plus the meta keys) around whatever was already there.
5. Rewrites Obsidian-style wikilinks to relative markdown links only when the target file is part of the imported set:
   • [[Page]] → [Page](Page.md)
   • [[Page|alias]] → [alias](Page.md)
   • [[Page]] with no matching file → left intact (no broken-link fabrication).
   • ![[image.png]] embeds → left intact (this importer does not yet pull attachments through; that is a follow-up).
6. Derives a title from the first H1 heading (after any frontmatter block); falls back to the filename without extension.
7. Records createdAt / updatedAt from the file's birthtime / mtime.

Wikilink resolution

Wikilink targets are matched case-insensitively by basename (the filename without extension), against the set of files this run is importing. Two files in different folders with the same basename trigger a log line and resolve to the first one discovered — keep names unique per vault if that matters to you.

The rewritten link uses a POSIX-relative path computed from the source file's location, so a wikilink in notes/inbox/today.md pointing at notes/refs/Page.md becomes [Page](../refs/Page.md) and survives the host preserving folder layout.

What it does not do

• It does not flatten anything — collisions are preserved as nested files.
• It does not pull image / asset attachments. Embed-style wikilinks (![[…]]) are left intact.
• It does not modify frontmatter. If you want a source: generic key, set it in the source file before importing.
• It does not look at .textbundle packages specially — they walk like any other directory.

Source

• apps/electron/importers/generic/index.ts — the importer module, including the exported rewriteWikilinks helper.

Acceptance checklist (#250)

• User picks a folder.
• All .md, .markdown, .txt files imported preserving relative paths.
• Wikilinks [[Page]] rewritten to [Page](Page.md) when the target exists in the imported set.
• Frontmatter preserved verbatim.
• Docs at docs/importer-generic.md (this file).