Closes#2332 item 1 (workspace awareness — agents don't surface
platform-native tools up front).
The dogfooding session surfaced that agents weren't using A2A
delegation, persistent memory, or send_message_to_user. The tools
were registered AND documented in the system prompt — but only in
sections #8 (Inter-Agent Communication) and #9 (Hierarchical Memory),
which agents read AFTER they've already started reasoning about a
plan from earlier sections.
This adds a tight inventory at section #1.5 (immediately after
Platform Instructions, before role-specific prompt files) — every
tool name + its short description in a bulleted block. Detailed
when_to_use docs in sections #8/#9 stay; this preamble is the
elevator pitch ("you have these"), the later sections are the
manual ("here's when and how").
Generated from `platform_tools.registry` ToolSpecs — every tool's
`name` + `short` flow through automatically, no manual sync. A new
`get_capabilities_preamble(mcp: bool)` helper in executor_helpers
mirrors the existing get_a2a_instructions / get_hma_instructions
pattern.
CLI-runtime agents (mcp=False) get an empty preamble — they see
_A2A_INSTRUCTIONS_CLI's hand-written subcommand vocabulary further
down, and the registry's MCP tool names would conflict.
Tests:
- test_capabilities_preamble_appears_in_mcp_prompt: header present
- test_capabilities_preamble_lists_every_registry_tool: every
a2a + memory tool from registry shows up (drift catches at test
time — adding a new tool to registry surfaces here automatically)
- test_capabilities_preamble_precedes_prompt_files: ordering
invariant (toolkit before role docs)
- test_capabilities_preamble_skipped_for_cli_runtime: empty when
mcp=False
All 40 prompt + platform_tools tests pass.
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