fix(mcp): keep fresh-worktree launch process-local

[saariuslystoned]

Why

A real Puppet-owned AGY CLI session in a fresh isolated worktree could not load the repository-local computer-use MCP server. The worker attempted to repair that by trusting the worktree mise config, which would mutate operator-global trust state.

What changed

• prefer an already-exact ambient Node 22.23.1 plus pnpm 10.33.0 toolchain;
• otherwise invoke mise with --no-config and explicit node@22.23.1 and pnpm@10.33.0 versions;
• add a deterministic stub-mise regression proving the fallback never calls trust or loads .mise.toml;
• teach both synced skill copies to route observations explicitly by display_id on multi-display systems and to treat window-cropped capture as unsupported.

This hardens the immediate launcher failure and advances the existing multi-monitor work in #4 and #5 without pretending window-targeted capture already exists.

Verification

• pnpm check
• pnpm test (52/52)
• ./bin/agy-computer-use production-ready