feat: add "Import as template" to File Tree context menu

[Adityakk9031]

Resolves #590

Description

This PR addresses the feature request to easily convert existing documents into templates. It adds an Import as template option directly to the right-click context menu of standard markdown files in the File Tree.

Users can now choose to:

• Keep original file: Copies the content and its frontmatter directly into a new template within .ok/templates/.
• Convert (delete original): Copies the file to the templates directory and safely removes the source document, updating the UI automatically.

Changes Made

• API (Core & Server): Added a secure POST /api/template/import endpoint (handleTemplateImport) which atomically extracts the source file's frontmatter, manages potential disk/sync conflicts, and persists the new template.
• Frontend (FileTree.tsx & Client API): Added the nested context menu items using the Lucide FileKey icon, bound them to a new importTemplate client wrapper, and handled immediate UI state cleanups (closing open tabs and removing deleted source files from the view).
• Changeset: Added a patch changeset for the release notes.

[CLAassistant]

All committers have signed the CLA.

[itsmistermoon]

Why is this being ignored 😭 it's the one thing I've been waiting to use OK

[tim-inkeep]

Hey @itsmistermoon, not ignoring it! This one's on me to review. @Adityakk9031 put together a real implementation here, so we want to give it a proper look rather than rush it. Will follow up on the PR shortly.

[tim-inkeep]

Thanks for this @Adityakk9031 — really useful feature and it maps cleanly onto how folder templates already work. I pushed a few commits to the branch to get it building and through our CI gates (the handler insertion had accidentally dropped the tail of handleTemplateMove, so the server package wasn't compiling; also added the i18n catalog extraction, route meta-test registrations, and a changeset, then rebased on main).

Two design questions before we merge:

1. The source title bakes into every instance. The import copies the source doc's frontmatter into the template's instantiated body, so title gets carried in — every new doc created from this template inherits the original file's exact title (make a template from "Q3 Planning" and every doc created from it is titled "Q3 Planning"). For a reusable template that's usually not what you want. Could we drop title from the instantiated frontmatter (keep it only in the template identity block) or make it a placeholder? Carrying description/tags over is fine.

[tim-inkeep]

2. "Convert (delete original)" deletes the source with no confirmation. It's one click inside a submenu and irreversible from the UI. Could we gate it behind a confirm step (reusing the existing delete-confirmation dialog)? "Keep original" is safe as-is; it's just the convert path that needs the guard.

[Adityakk9031]

@tim-inkeep have a look

[github-actions]

Your change is now on main. Thanks for contributing!

Because this repository is maintained through an internal mirror, GitHub shows this PR as closed rather than merged, but your commits are on the default branch with your authorship preserved. Closing it here to keep things in sync.