config: Phase 4 memory example block (commit #5)

Phase 4 commit #5 (final) per docs/PHASE4.md §12. Documentation-only;
commented-out example showing:
  - inject_max_chars (cap on startup injection; default 2000)
  - summarizer_model (which configured model :memory summarize uses)

The block is OFF by default. The :memory meta surface (:remember,
:memory list/forget/clear/inject/summarize) works without the block —
items persist to <history.dir>/memory.jsonl regardless. The block only
configures the injection-into-system-prompt behavior + summarizer model
choice.

Phase 4 implementation complete:
  #1 199dd87  history.lua memory store + ffi/libc.lua flock
  #2 c1a5c73  context.lua [background] block (suppressed in Norris)
  #3 3b074af  repl.lua memory handle + :remember + :memory meta
  #4 f22d21d  :memory summarize — LLM candidate extraction
  #5 (this)   config.lua memory example block

Phase 4 verify-partial:
  - history memory round-trip tests: add/forget/load all green
  - flock single-writer enforcement verified
  - context composition order (DEFAULT → [background] → NORRIS) +
    Norris suppression all green
  - End-to-end persistence across boots: :remember on boot 1 visible
    on boot 2 as injected memory items
  - :memory forget id-not-active surfaces clean status (N1)
  - :memory clear with [y/N] confirm gate works
  - :memory summarize wire-correct against fast model (candidate
    parsing tolerates bullets; per-candidate y/N/edit prompts fire)

Verify-pending: real-model summarizer quality test (deep/cloud);
multi-process flock contention test; long-running :memory inject
race with running broker stream.

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

config.lua

@@ -123,4 +123,27 @@ return {
     --     -- Default 8. Bump for long-running goals; cap low for testing.
     --     max_norris_steps = 8,
     -- },
+
+    -- Phase 4 (docs/PHASE4.md): cross-session memory.jsonl + startup
+    -- injection + :memory management surface. The block is OFF by
+    -- default (no startup injection); uncomment to tune. Note that
+    -- :remember / :memory list / :memory forget / :memory summarize
+    -- all work without this block — they store to <history.dir>/
+    -- memory.jsonl regardless. The block only configures the
+    -- injection-into-system-prompt behavior at startup.
+    --
+    -- memory = {
+    --     -- Cap on total characters injected at startup. ~2000 chars ≈
+    --     -- 500 tokens. LRU-by-ts selection if your memory.jsonl has
+    --     -- more recent items than fit. Older items remain in the
+    --     -- file; only injection is bounded. Suppressed entirely in
+    --     -- Norris mode (R-C1).
+    --     inject_max_chars = 2000,
+    --
+    --     -- Which configured model to use for :memory summarize.
+    --     -- Defaults to the active model when nil. Use "fast" for
+    --     -- speed; "deep" or "cloud" for better extraction quality
+    --     -- (cloud may have variable cost per session).
+    --     summarizer_model = "fast",
+    -- },
 }