research: finalize #18 read-path + upstream pool audit

[Skywind5487]

Research artifact

Canonical finding: docs/research/issue-39-read-ctx-upstream-audit.md

Refreshes the earlier #39 exploration against:

• fork dev@fa5ed679cc6559c619038f327e6276f4b7e8d735
• upstream NousResearch/hermes-agent@main@fc9cbc872d8050c22f1192b16bc5ff4aed471e10

Final research decision for #18

1. Import the accepted bounded SessionDB read pool first, using the two preserved fix(state,desktop,runtime): EMFILE cascade — bounded WAL read pool, orphan serve reap, nofile floor NousResearch/hermes-agent#83406 contributor commits (9cc5c463…, then 5eaabc9e…) rather than the unrelated whole bundle.
2. Then migrate only the remaining pure search/lookup projection reads; highest-value seam is get_compression_tip() because session listing/search already uses _read_ctx() and then re-enters the writer lock during compression-tip projection.
3. Fix fork-only SessionDB(read_only=True) message-CJK serving parity without marking the read-only attach as a CJK rebuild worker.
4. Add RED-first peak-pool, writer-lock convoy, real CJK serving, semantic-equivalence, and contention tests.

Upstream status reconciliation

• perf(state): read-path split — per-thread read-only connections for recall reads NousResearch/hermes-agent#73344 / fix(dashboard): preserve maintenance writes on read polling (salvage #67903) NousResearch/hermes-agent#76895 / fix(state): route session-resume reads through the WAL read-only connection (salvage #73539) NousResearch/hermes-agent#77803: merged and already absorbed by the fork.
• fix(state,desktop,runtime): EMFILE cascade — bounded WAL read pool, orphan serve reap, nofile floor NousResearch/hermes-agent#83406: merged and present in current upstream main, absent from fork; authoritative pool design.
• state: pool SessionDB read connections instead of leaking one per (SessionDB x thread) NousResearch/hermes-agent#76700: closed unmerged; salvaged into fix(state,desktop,runtime): EMFILE cascade — bounded WAL read pool, orphan serve reap, nofile floor NousResearch/hermes-agent#83406.
• fix(state): bound reusable SQLite WAL readers NousResearch/hermes-agent#81082: closed unmerged; explicitly closed as superseded after the same lifecycle fix + peak bound landed upstream.
• fix(state): use _read_ctx() for handoff reads to avoid SQLite errmsg-… NousResearch/hermes-agent#73803 / fix(state): unlocked reads on the shared SessionDB writer connection destroy turns as session_persistence_failed NousResearch/hermes-agent#90734 / fix(state): evict a poisoned pooled read connection instead of requeuing it NousResearch/hermes-agent#85255 / fix(state): disable WAL read pool when journal mode is unknown NousResearch/hermes-agent#87044: open, unmerged; evidence/follow-up only, not cherry-pick authority.

Research-only PR. No #18 implementation code is included here.

Final recon: RECON FINAL @ fa5ed679…

Refs #18
Refs #39

[github-actions]

૮ >ﻌ< ა ci review

_{ran on c7dcd98 — research: refresh #18 read-path audit against current upstre}

all good!