fix: document upsert project_id, truncation budget, and Ollama model matching

- regenerator: Include project_id in the ON CONFLICT UPDATE clause for
  document upserts. Previously, if a document moved between projects
  (e.g., during re-ingestion), the project_id would remain stale.

- truncation: Compute the omission marker ("N notes omitted") before
  checking whether first+last notes fit in the budget. The old order
  computed the marker after the budget check, meaning the marker's byte
  cost was unaccounted for and could cause over-budget output.

- ollama: Tighten model name matching to require either an exact match
  or a colon-delimited tag prefix (model == name or name starts with
  "model:"). The prior starts_with check would false-positive on
  "nomic-embed-text-v2" when looking for "nomic-embed-text". Tests
  updated to cover exact match, tagged, wrong model, and prefix
  false-positive cases.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/documents/regenerator.rs

@@ -145,6 +145,7 @@ fn upsert_document_inner(conn: &Connection, doc: &DocumentData) -> Result<bool>
           is_truncated, truncated_reason)
          VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9, ?10, ?11, ?12, ?13, ?14, ?15)
          ON CONFLICT(source_type, source_id) DO UPDATE SET
+           project_id = excluded.project_id,
            author_username = excluded.author_username,
            label_names = excluded.label_names,
            labels_hash = excluded.labels_hash,