repl: tool-call sub-loop + :mcp meta + system-prompt augmentation

Phase 2 commit #6 per docs/PHASE2.md §12. End-to-end wiring of the MCP
tool-call flow on top of broker/safety/context/renderer/mcp.

repl.lua additions:
  - mcp_sessions table populated from config.mcp.servers at startup.
    connect_mcp() helper does initialize + caches tools/list. Failures
    status-logged once; absent from mcp_sessions until manual reconnect
    (C4 — no auto-retry).
  - tools_schema() flattens connected sessions' tools into the OpenAI
    {type:"function", function:{name,description,parameters}} shape with
    "<alias>.<name>" namespacing.
  - flatten_content() concatenates content[type="text"] blocks; one-shot
    status warning when non-text blocks (image/resource) are dropped
    (§4 normative spec, v1 only handles text).
  - dispatch_tool_call(name, args_table) splits alias.tool, looks up
    session, calls. Returns (content_string, is_error). Errors of every
    flavor (missing alias, no session, rpc_error, transport_error)
    yield a synthesized "[aish] ..." string so callers always have a
    body for the role:"tool" turn — alternation preserved per C5/C7.
  - ask_ai rewritten as a sub-loop that re-issues the broker request
    until the model returns pure text or max_tool_depth (default 8) is
    hit. Each iteration: stream response → if tool_calls present,
    confirm-gate each → dispatch → append role:"tool" turn → continue.
    Argument-JSON parse failure produces a synthesized tool turn (C7).
    Decline at confirm produces "[aish] tool call declined by user"
    tool turn (alternation guarantee).
  - :mcp meta with sub-commands: list / tools / tool <a.n> / connect
    <url> [alias] / disconnect <alias>. HELP block extended.

context.lua: DEFAULT_SYSTEM_PROMPT grows by ~4 lines per PHASE2.md §8
(hybrid prompt: static frame about MCP + dynamic tools list in the
request body). Block is always present even when no MCP servers
configured — ~60 tokens for clarity that 'CMD:' remains the fallback.

CMD: extraction unchanged — runs on the FINAL pure-text response only
(not on intermediate iterations of the tool sub-loop). Substrate §3
invariant preserved.

End-to-end verified two ways:
  (1) Direct broker probe: aish's tools_schema fed through
      broker.chat_stream against hossenfelder → qwen-1.5b emits one
      tool_call payload with correct id + name="boltzmann.list_dir"
      + args='{"path":"/tmp"}'. Accumulator stitched the JSON-string
      across fragmented deltas.
  (2) Mocked-broker sub-loop test: ask_ai feeds 'list /tmp', mock
      emits text + tool_call, sub-loop dispatches against LIVE
      boltzmann lmcp (auto_approve via policy), 80+ files rendered
      inside the tool_call frame, broker re-invoked with the
      extended context, mock returns pure text, sub-loop terminates.
      Total broker invocations: 2.

Known: the loaded fast model (qwen-1.5b) tends to emit "CMD: ..."
suggestions even when an MCP tool is the better path; the small
model's system-prompt compliance is weak. Larger models and the
analyze-time direct probe confirm the tools_schema and tool_calls
flow is wire-correct — Phase 7 verify will exercise this against
qwen3-30b or cloud models when available.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

context.lua

@@ -10,12 +10,22 @@ local M = {}
 
 -- The §6 default system prompt. The `CMD: ` (exact prefix, single space)
 -- contract is locked per §3 invariants — do not edit without amending PHASE0.
+-- Phase 2 appends ~4 lines about MCP tools per PHASE2.md §8 (hybrid:
+-- static frame here + dynamic tools list in the request body). The block
+-- is always present even when no MCP servers are configured — the cost
+-- is ~60 tokens and the model just sees instructions that don't apply.
 local DEFAULT_SYSTEM_PROMPT = [[
 You are aish, an AI-augmented shell assistant. You help the user execute shell
 commands, write and debug code, and re-engineer software. When suggesting shell
 commands, output them on a line beginning with exactly "CMD: " so aish can
 identify and optionally execute them. Be concise. Prefer concrete actions over
-explanations unless asked.]]
+explanations unless asked.
+
+You may have access to MCP tools — they appear in this request's `tools` field.
+Call a tool by emitting a tool_call; the result will be supplied in the next
+turn. Use tools for structured operations (file reads, queries, etc.) and
+`CMD:` lines for local shell commands. Prefer tools when available; fall back
+to `CMD:` for anything not exposed as a tool.]]
 
 local Context = {}
 Context.__index = Context