bug(unic-archon-dlc): `synthesize` dedupes before identity is assigned and merged across two files against its own rule

Observed

unic-dlc-pr-review.yaml:376: synthesize has "no prior-iteration awareness — that is reconcile's job". :390: it dedupes "same file + near-identical title across the two axes → keep the highest-confidence one". In run 3 iteration 2 it cut 13 to 11 and dropped the two twins that would have matched priors (eef8a1fb standards/User2.tsx, c30c2e7d spec/styles.css), keeping the non-matching twin each time; the second merge joined styles.css:88 with Card.tsx:21, two files, against :390.

reconcile then matched both priors through the surviving twins by semantic title, so no wrong verdict resulted this time. Latent, not demonstrated.

Why it matters

The dedup step is upstream of the identity step and blind to it, so an arbitrary dedup choice can destroy cross-iteration continuity. When reconcile's fallback does not rescue it, a still-present finding posts as a prior fixed plus an unrelated new.

Evidence

• Findings register, § "G. What run 3 taught about the instrument", row G6: https://github.com/unic/unic-agents-plugins/blob/bcf688a/docs/research/2026-08-31-dlc-run-2-findings.md
• Run record and harvested artefacts: ~/Desktop/run3-parked/ on the maintainer's machine (artefacts-908e3735…/findings/review.json (14) vs findings.json (11); .remember sighting 10 (the node's own note: "deduped 1 overlap …"))
• Dispatch record: #457 from comment 5698289748 down

Not decided

• Dedup after reconcile assigns identity, or make synthesize prefer the twin whose aspect and file match a prior.
• Whether a cross-file merge is ever legitimate.

Filed 2026-09-17 by wayfinder-orchestrator-10 from run 3's measurements. needs-specs: grill before dispatch.

Start with unic-dlc-pr-review.yaml lines 376-390, then inspect the run 3 findings and dispatch records linked in the issue. Define the deduplication and identity behavior, including whether cross-file merges are valid, and provide evidence that the chosen rule preserves prior matching.