Notes syndicate to social as full body via a dedicated dlvr.it feed

## Summary

Syndicate note posts to the existing social profiles as their full body — not a title+link teaser — through a dedicated notes feed and dlvr.it source.

## Motivation

A note's value is the body itself; the current `rss.xml` → dlvr.it path (ADR 0001) posts title + hook + link, which buries a note. IndieWeb notes syndicate as full text. dlvr.it already forwards feeds to the social profiles, so a notes feed carrying the full body, on the same profiles, extends the mechanism — the same second-source pattern as #292. #191 is held pending this.

## Scope

- Generate a notes-only feed (e.g. `notes.xml`) filtered by the note marker (format issue), with the full post body as the item content/`description`.
- Add it as a dlvr.it source on the existing profiles; confirm free-tier source/rate limits before it trips the paid-tier "fourth surface" trigger (ADR 0001).
- De-dupe against the main feed so notes don't double-post (ties to the format issue's main-feed decision).
- Amend ADR 0001: syndication now includes a full-body note source alongside the title+link blog feed.
- Document under `docs/how-to/`, beside the existing syndication how-to.

## Acceptance criteria

- [ ] Publishing a note posts its full body to the connected profiles automatically.
- [ ] Notes don't double-post via the main feed.
- [ ] dlvr.it free-tier limits confirmed sufficient, or the tier change is called out.
- [ ] ADR 0001 amended; `docs/how-to/` updated.

## Additional context

- Blocked by the note format issue.
- Same second-source dlvr.it pattern as #292.