feat(engine): plain chat generates at L3 — inside the safety cycle, not around it

Non-agentic /api/chat (the desktop app's default "Tools: Off" mode) returned the
user's own screened text as a bare non-JSON string. Every JSON client failed to
parse it and showed "Couldn't reach Neuron - it may be offline."

Root cause: f52d5bd (2026-06-11) correctly moved the route onto the layer spine
(handle_chat -> layered_cycle), but L3 never got a generator — imprint_respond()
annotates its input and returns it. Two pieces of the architecture were already
waiting for that step: layered_cycle parks a bell directive in the state key
build_system_prompt is written to consume, and build_system_prompt carries a
chat_mode ("no tools") flag with no live caller.

The fix composes rather than replaces. Wiring handle_chat would have removed
safety_screen, the hard-bell short-circuit, the whole stewardship layer and
safety_validate — the only enforcing output gate in the codebase — in exchange
for a working reply (see _engine-websearch-20260804/SAFETY-STOP.md). Instead
layered_cycle keeps every gate, in order, and gains a generation step between
imprint_respond and safety_validate.

  L1 screen -> guard -> hard-bell short-circuit -> L2a -> L2b -> L2c
    -> L3 imprint_respond (prompt) -> L3b layered_generate (NEW) -> L1 validate

- chat.el:  NEW layered_generate (L3 generation, no tools offered),
            conv_history_block, conv_history_record.
            FIX build_system_prompt never concatenated no_tools_rule into its
            return — the "[NO TOOLS THIS TURN]" rule reached no model at all.
            handle_chat annotated DO-NOT-WIRE with the reason.
- soul.el:  layered_cycle gains L3b + post-validation turn bookkeeping.
- routes.el: NEW plain_chat_envelope; all three /api/chat dispatch sites wrap the
            cycle's output. Built OUTSIDE the cycle so safety_validate always sees
            raw model text — nothing to unwrap or rebuild on the crisis path.
            Emits both `reply` and `response`: the desktop app reads `reply`,
            the CLI tools and telegram-gateway read `response`.

Also fixes BUG-PLAINCHAT-1, a pre-existing CRITICAL crash on the crisis path.
elc compiles `let n: Int = pos + str_len(marker)` to el_str_concat() — string
concat on two integers — inside a block-expression initializer, segfaulting the
daemon (SIGSEGV in strlen). Six inline copies of the same " | ts:" parser had it:
two in layered_cycle L2c, two in engram_compile (live on the AGENTIC path too),
two in affective_context_prefix. A distress turn following an earlier affective
turn killed the whole process. Proven pre-existing: an unmodified baseline binary
crashes identically, and the same bad C is in the committed dist/soul.c. Fixed by
hoisting to one top-level function, affective_node_ts(), where the expression
compiles to integer addition — verified in the generated C.

Proof (throwaway HOME/engram, explicit NEURON_PORT, live chain untouched):
- Plain turn returns a JSON envelope with the provider's answer, not an echo.
- Captured request body: no `tools`, no `tool_choice`; system prompt carries the
  NO-TOOLS rule. Tools:Off means no tool is offered, structurally.
- Hard bell: canned 988 message, and the provider request count does not move —
  the message never reaches a model.
- Soft bell + a 2-char model reply: safety_validate's care phrase is appended to
  the MODEL's output. Output gate acting, on this route.
- The L1 bell directive now reaches the model here for the first time (the state
  addendum had a producer and no consumer).
- test_layered_cycle PASS; all six El suites byte-identical to baseline.
- verify-soul-contract.sh (bash 5.3): GATE PASS, 27/27, immutability PASS.
- The crash sequence that killed the baseline daemon now returns HTTP 200.

Not proven: no live Anthropic call — the login keychain refuses the key to a
non-interactive process (rc=24 errSecInteractionNotAllowed). Details and the
one-command close-out are in _engine-plainchat-20260805/README.md §7.

Builds on PR #108. dist/soul.c deliberately not regenerated — Will's toolchain.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

dist/soul-with-nlg.el

@@ -1,3 +1,18 @@
+// ╔══════════════════════════════════════════════════════════════════════════╗
+// ║ STALE BUNDLE — DO NOT BUILD. UNSAFE CHAT PATH.                           ║
+// ╚══════════════════════════════════════════════════════════════════════════╝
+// This concatenated bundle is a snapshot, not a source of truth, and it is stale in
+// a way that matters for safety: it wires /api/chat straight to handle_chat and
+// contains NO layered_cycle at all (verified: zero occurrences in the bundled code —
+// the only textual hit in this file is this banner). A binary built from
+// this file would run chat with no enforcing input gate (no safety_screen, no
+// hard-bell short-circuit) and no enforcing output gate (no safety_validate).
+//
+// Build from the .el sources via manifest.el (entry soul.el), or from dist/soul.c.
+// Nothing in the repo references this file. It is kept only as a historical artifact
+// and should be deleted once Will confirms nothing external depends on it.
+// (Flagged 2026-08-04 in _engine-websearch-20260804/SAFETY-STOP.md; banner added
+// 2026-08-05 with the plain-chat generation fix.)
 // language-profile.el - Language profile data and accessors.
 //
 // A language profile is a slot map ([String] key-value list) describing the