fix(#3384): strip mcp__* tool grants from zcode-installed subagents (#3483)

* fix(#3384): strip mcp__* tool grants from zcode-installed subagents

ZCode's dispatcher treats every mcp__<server>__* entry in an agent's
tools: frontmatter as a required MCP server and hard-fails the subagent
spawn (CONFIGURATION_ERROR) when it is not connected, whereas Claude Code
treats the same grants as an optional allowlist. ZCode shared Claude's
verbatim agents copy (converter: null), so all 8 MCP-granted agents
failed to spawn out of the box with zero MCP servers configured.

Add convertClaudeAgentToZcodeAgent — a line-surgical converter that
filters mcp__* entries out of the frontmatter tools: grant list (both
inline comma and YAML block-list shapes) and preserves every other byte.
Declare it on both of zcode's capability.json agents entries and cut
zcode over to the descriptor-driven agents path
(_DESCRIPTOR_AGENTS_RUNTIMES) so the legacy inline loop stops
deleting+re-copying the converted agents raw. Claude Code, Kimi, and
Gemini install behavior is unchanged.

* chore(#3384): link changeset fragment to pr 3483

---------

Co-authored-by: sim <sim@local>

.changeset/sharp-moles-howl.md

@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 3483
+---
+ZCode installs now strip mcp__* tool grants from installed GSD subagents at install time. ZCode's dispatcher treats every mcp__<server>__* entry in an agent's tools: frontmatter as a required MCP server and hard-fails the subagent spawn (CONFIGURATION_ERROR) when it is not connected, so /gsd-quick --full and plan/execute-phase flows failed out of the box with zero MCP servers configured. Installed ZCode agents now declare only core tools; MCP tools remain available when servers are connected. Claude Code installs are unchanged.