docs: update robot-docs manifest and agent instructions for since-last-check

Updates the `lore robot-docs` manifest with comprehensive documentation
for the new since-last-check inbox feature, enabling AI agents to
discover and use the functionality programmatically.

robot-docs manifest additions:
- since_last_check response schema with cursor_iso, groups, events
- --reset-cursor flag documentation
- Design notes: cursor persistence location, --project filter behavior
- Example commands in personal_dashboard section

Agent instruction updates (AGENTS.md, CLAUDE.md):
- Added --mrs, --project, --user flags to command examples
- Added --reset-cursor example
- Aligned both files for consistency

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -645,8 +645,12 @@ lore --robot embed
 # Personal work dashboard
 lore --robot me
 lore --robot me --issues
+lore --robot me --mrs
 lore --robot me --activity --since 7d
+lore --robot me --project group/repo
+lore --robot me --user jdoe
 lore --robot me --fields minimal
+lore --robot me --reset-cursor
 
 # Agent self-discovery manifest (all commands, flags, exit codes, response schemas)
 lore robot-docs