docs: remove bm watch from v0.19.0 release notes

The watch command was removed from the codebase — drop the section
from the release notes so it doesn't advertise a non-existent feature.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: phernandez <paul@basicmachines.co>

Author: phernandez

docs/releases/v0.19.0.md

@@ -92,15 +92,6 @@ All MCP tools now support `output_format="json"` for machine-readable responses.
 - `build_context` defaults to `"json"` with slimmed payloads (redundant fields stripped)
 - CLI tool commands support `--format json` flag
 
-### `bm watch` Command
-
-New CLI command for real-time file watching and sync.
-
-```bash
-bm watch                    # Watch default project
-bm watch --project research # Watch specific project
-```
-
 ### Structured Metadata Search
 
 New `search_by_metadata` tool for searching by frontmatter fields.