feat(cognition,#1385): generate_response PR-1 — pure types + prompt builder + identity-reminder template

[joelteply]

Summary

Oxidizer for AIDecisionService.generateResponse (TS, see src/system/ai/server/AIDecisionService.ts:316-452 + buildResponseMessages helper at lines 439-540). Sibling to the just-completed check_redundancy stack (#1375 — PRs #1377/#1381/#1383 MERGED). This is the last remaining TS-side AI logic in AIDecisionService.ts.

What this ships (PR-1 scope — pure, atomic)

• GenerateResponseRequest (ts-rs) — { context, model?, temperature?, max_tokens?, timeout_ms? }
• GenerateResponseResult (ts-rs) — { text, model, response_time_ms, timestamp, tokens_used? }
• TokenUsage (ts-rs) — { input, output, total }
• build_response_messages(&AIDecisionContext, current_time_ms) -> Vec<ChatMessage> — pure. Composes:
  1. System-prompt message (from context.system_prompt)
  2. Conversation history with [HH:MM] time prefix + hour-gap markers (⏱️ N hour passed)
  3. Identity-reminder system message at end
• build_identity_reminder(persona_name, members, current_time) -> String — pure. Canonical ~50-line critical-topic-detection prompt template (byte-for-byte parity with TS modulo substitutions).
• extract_room_members(system_prompt) -> &str — pure. Pulls Current room members: ... from a system prompt body.
• format_current_time(ms) -> String — pure. UTC MM/DD/YYYY HH:MM.
• format_time_prefix(Option<ms>) -> String — pure. UTC [HH:MM] .
• hour_gap_marker(gap_ms) -> Option<String> — pure.

NOT in this PR

• PR-2: cognition/generate-response IPC handler — async composer that calls build_response_messages → AI provider (existing local Qwen router) → result with timing + tokio::time::timeout replacing the TS Promise.race.
• PR-3: TS shim — AIDecisionService.generateResponse delegates to RustCoreIPCClient.cognitionGenerateResponse.
• PR-4: Delete dead TS — buildResponseMessages + inline identity-reminder template (~250 LOC removed). After PR-3 + PR-4, AIDecisionService.ts is pure slot-coordination + shim code.

Discipline

• All pure functions; caller passes current_time_ms so tests are deterministic.
• UTC time formatting removes hidden TZ dependency the TS version had (server timezone was leaking into model prompts via toLocaleDateString).
• Members extraction falls back to literal "unknown members" string — matches TS exactly so prompt machinery doesn't regress.
• Empty system_prompt treated as missing (avoids emitting an empty system row that some providers reject).
• Identity-reminder template byte-for-byte parity with TS modulo substitutions.
• Conversation types reused from gating stack (no new shapes invented for shared concepts).

Tests (29 — 26 logic + 3 ts-rs export)

format_current_time (2): mm/dd/yyyy hh:mm UTC at known timestamp, epoch zero boundary.

extract_room_members (4): happy path, no trailing newline, missing prefix→fallback, empty after prefix→fallback.

format_time_prefix (2): HH:MM UTC render, None→empty.

hour_gap_marker (3): under threshold→None, 1 hour singular, 2+ hours plural.

identity_reminder (3): embeds persona+members+time, preserves four-step protocol, preserves time-gap heuristic line.

build_response_messages (12): system+history+identity order, omits system when None, omits system when empty string, hour-gap marker for >1h gaps, no marker under one hour, gap tracking ignores clockless messages (TS parity), name fallback, members extracted for identity reminder end-to-end, unknown members fallback when prompt missing line, no system prompt→unknown members fallback, preserves role strings as-is, empty history.

ts-rs exports (3): all 3 wire types pin barrel consistency.

Full cognition regression: 325/325 pass.

Refs

• oxidizer: migrate AIDecisionService.generateResponse to Rust cognition/generate-response #1385 — sub-card just filed for this oxidizer
• TS-side AI logic that violates 'TS is thin glue' directive — umbrella triage #1248 — umbrella: TS-side AI logic violates 'TS is thin glue' directive
• Sibling: oxidizer: migrate AIDecisionService.checkRedundancy to Rust cognition/check-redundancy #1375 check_redundancy stack (MERGED PRs feat(cognition,#1375): check_redundancy PR-1 — pure types + prompt + parser #1377, feat(cognition): wire check redundancy IPC #1381, feat(cognition): delegate redundancy shim to rust #1383)
• Sibling: rate_proposals stack refactor(cognition,#1289): rate_proposals PR-1 — Rust types+prompt+parser slice #1290/refactor(cognition,#1289): rate_proposals PR-2 — IPC handler + orchestrator #1291/refactor(cognition,#1289): rate_proposals PR-3 — delete dead TS adapter (no production callers) #1293 (MERGED)
• Sibling: should_respond.rs (already oxidized — evaluateGating arm)

Test plan

• cargo test --package continuum-core --lib --features metal,accelerate cognition::generate_response:: — 29/29 pass
• cargo test --package continuum-core --lib --features metal,accelerate cognition:: — 325/325 pass (no regressions)
• Pre-push TS clean, ESLint baseline held, Rust compile clean
• CI green
• PR-2 IPC handler stack on top (separate PR)

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