feat: pick the paper's PaperBell project when scaffolding it

[SongshGeo]

What

The New PaperBell paper project… modal now asks which PaperBell project the paper is a deliverable of, and writes the answer as a top-level project: key in the frontmatter of every draft index note it creates.

docs/PAPERBELL_SUITE.md has always described outputs linking back to their project via project: <acronym>, but nothing wrote it — so a paper scaffolded into 50 - Outputs carried no field naming its project, and Project Manager could not recognize it as a deliverable.

Decisions

Where	Note frontmatter only — metadata.json stays pure publication metadata
Value	Plain acronym (project: ColMemo), not a wikilink
No host / old host	Degrades to a free-text box; no folder scanning, no new settings
Scope	New-paper modal only

project (the project's acronym) and _longform.acronym (the paper's own, used for PDF filenames) are different values with different jobs; the UI labels them apart. An empty selection omits the key entirely rather than writing an empty project:.

Host integration — a proposal, inert today

The project list comes from a proposed projects scope (requestProjects(), paperbell:projects-changed, PPBProject). No shipped host implements it. It is vendored into src/paperbell/shared-config.ts and flagged there as ours, with the client methods declared optional and every caller gating on capabilities and typeof method === "function" — so it stays completely inert against the 0.4.4 host. PPB_SCHEMA_VERSION deliberately stays at 1 so the "host schema is newer than vendored" warning keeps working for a real upstream v2.

docs/PROPOSAL_PROJECTS_SCOPE.md writes it up for the host team, including the two questions that matter more than the API itself:

1. Which frontmatter shape does Project Manager actually query? We write a plain acronym per the existing convention. If it wants [[wikilink]], changing the writer is one line — migrating users' notes is not.
2. One paper is up to four notes, all carrying the same project:. Dedupe key is longform.title, identical across a paper's drafts.

MAINTAINING.md records the re-vendoring hazard: a straight copy from upstream, for any reason, deletes the proposal block and breaks the build.

Verification

• 438 tests pass (22 new), lint 0 errors, production build OK.
• Degradation paths covered by unit tests: host absent, host too old, capability missing, consent denied, ok: false, host throws.
• test/paperbell/host-conformance.test.ts gains a block that stays skipped today and arms itself once a host bundle carrying requestProjects is installed.

Still owed (manual, needs a real vault): confirming the new top-level project: doesn't affect strip-frontmatter / pandoc export. It sits outside the longform: block and goes through the existing whole-block strip, so no impact is expected — but it hasn't been run in Obsidian.

🤖 Generated with Claude Code