fix(mcp): case-insensitive agent name in diary_write/diary_read (#1243)

`tool_diary_write` stored the `agent` metadata verbatim after `sanitize_name`
(which preserves case), while `tool_diary_read` filtered by exact match —
so writing as "Claude" and reading as "claude" silently returned zero rows.

Both endpoints now lowercase `agent_name` immediately after sanitization.
The default per-agent wing slug is also stable across casings since it's
derived from the same normalized form.

Behavior change: entries written prior to this fix under mixed-case agent
names will not match the new lowercase filter; documented under v3.3.5
in CHANGELOG with a `mempalace repair` pointer.

Adds a regression test (`test_diary_read_case_insensitive_agent`) and
updates the existing `test_diary_write_and_read` to assert the new
lowercase agent identity.

Closes #1243

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,14 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 ---
 
+## [3.3.5] — unreleased
+
+### Bug Fixes
+
+- **`mempalace_diary_read` silently dropped entries on agent-name case mismatch.** `tool_diary_write` stored the `agent` metadata verbatim after `sanitize_name`, which preserves case, while `tool_diary_read` filtered by exact match. Writing as `"Claude"` and reading as `"claude"` (or vice-versa) returned zero rows. Both endpoints now lowercase `agent_name` immediately after sanitization, so reads are case-insensitive and the default per-agent wing slug is stable across casings. **Behavior change:** entries written prior to this fix under mixed-case agent names will not match the new lowercase filter; run `mempalace repair` if you need to migrate legacy diary metadata. (#1243)
+
+---
+
 ## [3.3.4] — unreleased
 
 ### Added