fix(embeddings): embed in the service, so every caller gets it (#2056)

A note or task created through MCP was not semantically searchable until the
next restart's backfill ran. Embedding fired at the five REST route handlers
and nowhere else; the MCP tools call the service directly, so they skipped it.

The shape of this bug is the reason to care: it is invisible on an instance
that redeploys constantly (this one does, per rule 46) and permanent on one
that doesn't. Rule 115 — the product has to stand up for the install that
restarts twice a year, not just for the one that restarts hourly.

Moved to services/notes.embed_note(), called from create_note and update_note,
and deleted from all five routes. Every caller — REST, MCP, recurrence,
snippets — now gets it by construction rather than by remembering.

Two things fall out of having one implementation instead of six:

- It uses note.user_id, the OWNER. The routes were inconsistent: some passed
  the caller's uid, some the owner's. On a shared record the caller's id mints
  a second embedding row that nothing reads.
- services/snippets.py's _embed_snippet existed only because snippets are
  created via MCP and the routes couldn't cover them. Every one of its four
  call sites goes through notes_svc, so the helper and its four calls are gone,
  along with the eight test patches that existed to neutralise it.

RuntimeError (no running loop — unit tests, scripts) and any indexing failure
are both swallowed: a write that succeeded must not be failed by its index.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

tests/test_snippet_unmerge.py

@@ -44,7 +44,6 @@ async def _run_unmerge(survivor, *, source_alive=None, restore=1):
         patch("scribe.services.trash.restore_entity", AsyncMock(return_value=restore)),
         patch.object(s.notes_svc, "update_note",
                      AsyncMock(return_value=survivor)) as upd,
-        patch.object(s, "_embed_snippet", MagicMock()),
     ):
         await s.unmerge_snippet(7, 1, 2)
     return upd.await_args.kwargs
@@ -127,7 +126,6 @@ async def test_a_purged_source_is_refused_and_the_survivor_is_untouched():
         patch("scribe.services.access.can_write_note", AsyncMock(return_value=True)),
         patch("scribe.services.trash.restore_entity", AsyncMock(return_value=None)),
         patch.object(s.notes_svc, "update_note", AsyncMock()) as upd,
-        patch.object(s, "_embed_snippet", MagicMock()),
     ):
         with pytest.raises(s.UnmergeError, match="purged"):
             await s.unmerge_snippet(7, 1, 2)
@@ -150,7 +148,6 @@ async def test_an_entry_without_attribution_is_refused_not_guessed():
         patch.object(s, "get_snippet", AsyncMock(side_effect=fake_get)),
         patch("scribe.services.access.can_write_note", AsyncMock(return_value=True)),
         patch.object(s.notes_svc, "update_note", AsyncMock()) as upd,
-        patch.object(s, "_embed_snippet", MagicMock()),
     ):
         with pytest.raises(s.UnmergeError, match="provenance"):
             await s.unmerge_snippet(7, 1, 2)