fix(gitea-mcp): address MCP tool issues from Sprint 6

Fixes #281 - Multiple MCP tool issues discovered during sprint execution

## Changes

1. **list_issues Token Overflow** (Issue 1)
   - Added `milestone` parameter to filter issues server-side
   - Reduces response size by filtering at API level instead of client-side

2. **Type Coercion for MCP Serialization** (Issues 2 & 4)
   - Added `_coerce_types()` helper function in server.py
   - Handles integers passed as strings (milestone_id, issue_number, etc.)
   - Handles arrays passed as JSON strings (labels, tags, etc.)
   - Applied to all tool calls automatically

3. **Sprint Approval Check Clarification** (Issue 3)
   - Updated sprint-start.md to clarify approval is RECOMMENDED, not enforced
   - Changed STOP/block language to WARN/suggest language
   - Added note explaining this is workflow guidance, not code-enforced

## Files Changed
- mcp-servers/gitea/mcp_server/gitea_client.py: Added milestone param
- mcp-servers/gitea/mcp_server/tools/issues.py: Pass milestone param
- mcp-servers/gitea/mcp_server/server.py: Type coercion + milestone schema
- plugins/projman/commands/sprint-start.md: Clarified approval check

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

mcp-servers/gitea/mcp_server/gitea_client.py

@@ -53,6 +53,7 @@ class GiteaClient:
         self,
         state: str = 'open',
         labels: Optional[List[str]] = None,
+        milestone: Optional[str] = None,
         repo: Optional[str] = None
     ) -> List[Dict]:
         """
@@ -61,6 +62,7 @@ class GiteaClient:
         Args:
             state: Issue state (open, closed, all)
             labels: Filter by labels
+            milestone: Filter by milestone title (exact match)
             repo: Repository in 'owner/repo' format
 
         Returns:
@@ -71,6 +73,8 @@ class GiteaClient:
         params = {'state': state}
         if labels:
             params['labels'] = ','.join(labels)
+        if milestone:
+            params['milestones'] = milestone
         logger.info(f"Listing issues from {owner}/{target_repo} with state={state}")
         response = self.session.get(url, params=params)
         response.raise_for_status()