D79 Wave 2: bottom-up summaries + placement (#165)

[fazpu]

Wave 2 of 3 for #165 — bottom-up section summaries and the placement hint, per plan/designs/e0_files_design.md §4.1.

What ships

• Summary seat REMEMBERSTACK_SUMMARY_MODEL (default z-ai/glm-4.7-flash): one-line summaries per section — leaves read their own direct blocks (oversized leaves shard at block grain), parents read their own blocks + child one-liners with balanced fan-in, the root reduction is one call with two fields (document summary + the D39 placement hint). Ceiling-driven reduction down to pairs; titles capped at every render site; a whitespace token estimate plus a hard character ceiling on every request; strict closed schemas with post-parse normalization (no max_length/pattern keywords that strict providers could 400 on).
• Per-section cache keyed on block hashes + child rendered lines + model/prompt/params/version: an edited leaf re-summarizes only its ancestor chain (proven by counting provider calls); degraded generations' sidecars join the cache pool so repairs re-pay nothing that succeeded.
• Generation identity is input/config identity only — model output hashes are OUT of the seed. First-write-wins genuinely holds (D12); a checker-only bump appends its check record and stops — zero summary calls, no minted generation, no pointer churn (test feeds different summary text under a different checker seat and asserts one generation, zero extra calls).
• Failure degrades to null summaries/placement per subtree, provenance-visible, never failing the document; P3 consumes real placement (slugged, depth-capped) from the current generation only.

Review trail

Codex implemented; Grok-4.5 (2 MAJOR / 5 MINOR) and Opus (6 MAJOR / 5 MINOR) reviewed independently — Opus reproduced three degradations with measurements (a 3000-word heading nulling a document with zero calls; 208KB of CJK passing a 58-"token" count; count-driven reduction giving up). The consolidated fix round (Codex) addressed every finding; Grok re-reviewed the fix diff: APPROVE, confirming all seven majors non-vacuously fixed. Final review and adjudication by Claude (the input-identity seed formulation and the §2.4 schema strip were the final-reviewer calls).

Gate

ruff clean, pyright 0 errors, 1003 passed including the Postgres-gated suites. No migration. Benchmarks and the tool catalog untouched.

• I have read and agree to the RememberStack Contributor License Agreement v1.0.

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
src/rememberstack/model
__init__.py
sections.py
src/rememberstack/profiles
selfhost.py					391-397, 423-424
src/rememberstack/spine
document_catalog.py					244
projection.py
src/rememberstack/workers
__init__.py
e0.py					741, 1131, 1169
e0_summary.py					389, 446, 462, 480, 489, 511, 513-515, 528, 539, 561, 580, 584, 598, 609, 611-626, 638-641, 651, 661, 850, 861, 872, 889, 901-911
Project Total

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