feat(mcp): page get_ownership_changes and summarize all changes

Between the two latest releases there are 1,568 holder changes. With only
`limit` (up to 2000, ~200 KB), agents that wanted them all overflowed
their tool output: Hermes then paged ticker by ticker (32 calls), and
opencode 1 and 2 did the same and timed out.

- `offset` pages through the rows; responses carry `offset` and
  `next_offset` (null after the last page). Pages cap at 300 rows
  (~40 KB); the over-limit error points to `offset` and `summary`.
- Rows come largest |delta| first, so the first page holds the moves
  that matter rather than tickers starting with A.
- `summary` covers every row: counts by change type, the number of
  tickers, and the ten tickers with the most changes.

The CLI's `ownership changes` is unchanged. tools.json and the website's
MCP pages are regenerated for the new description and parameter.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3syn2fN2LNo5pvTSqc6eh

web/src/content/docs/mcp/index.md

@@ -45,7 +45,7 @@ body, so the agent can decide whether to retry:
 | tickers per call (`get_quotes`, `compare_stocks`) | 20, duplicates removed |
 | `screen_stocks` `limit` | 200 |
 | `search_investors` `limit` | 100 |
-| `get_ownership_changes` `limit` | 2000 (default 200) |
+| `get_ownership_changes` `limit` | 300 per page (default 200); page with `offset` |
 | concurrent tool calls | 4 |
 
 ## Ownership data