Coordinating a multi-agent build: subagents cannot see the main session MCP tools

When orchestrating a big build as a boss/coordinator spawning subagents (Task/Agent tool) with beads for tracking, two things bit me and their fixes: (1) MCP tools authenticated in the MAIN session (e.g. a design-import MCP behind an interactive login) are NOT available to spawned subagents — the subagent ToolSearch finds nothing and it blocks. Fix: the coordinator fetches via the MCP itself, writes the artifacts to disk, and subagents read from disk. (2) Parallel subagents that edit files will clobber each other and produce half-written git commits. Fix: partition work by DISJOINT directories (engine/ vs render/ vs ai/ vs one file per screen), run those in parallel, and have the coordinator OWN the integration seams (define the exact interface/contract in the prompt, build the shared shell/registry/data-contracts yourself) so independent agents implement against a frozen API. Also: git add -A mid-run sweeps in other agents’ in-progress files — commit specific paths, or wait for each agent to report done + close its bead before committing. macOS bash is 3.2: no associative arrays (declare -A fails) which silently broke an ID-capture loop for batch issue creation.