docs: record embedding, neighbor, and inspect decisions

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/adr/0025-retrieval-inspect.md

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+# ADR-0025: Retrieval Inspect (Benchmarks full-page mode)
+
+## Status
+
+Accepted (implemented; Expected Answer strip amended)
+
+## Context
+
+Neighbor Expansion and Expansion Tree (ADR-0023) store per-question top-k hits with prev/next for Experiments, but operators cannot audit them well: Query is live-only, Experiment expand rows and HTML reports truncate or sample one question, and a new top-level Tab would stretch navigation. Operators need a dedicated, readable surface to choose a question and inspect retrieval in full detail. Operators also need the Expected Answer beside the Generated Answer to judge Similarity without leaving Inspect.
+
+## Decision
+
+- **Retrieval Inspect** is a **full-page mode inside the Benchmarks Tab** (not a new top-level Tab, not HTML-report-only).
+- Entry: **Inspect** action on an Experiment row (alongside Report).
+- Layout: **left question rail** (status for error / has Expansion Tree) + main pane with **Strategy picker** (default `fixed_size` when present), **side-by-side Generated | Expected Answer** strip with clear column headers (plain text, no word-diff), **full-width eval scores** under that strip, and a **vertical full-text Expansion Tree** (prev → hit → next per top-k hit; neighbors empty/N/A for other Strategies).
+- Expected column always renders; empty/missing `expected_answer` shows a muted “(no expected answer)”.
+- Visual language stays the existing Dashboard theme (ADR-0008); quality comes from hierarchy, spacing, and full text — not a separate brand.
+- Reads existing Experiment `per_question` payloads (`expansion_tree`, answers, `expected_answer`, scores); no new retrieval API required for v1.
+
+## Consequences
+
+- Benchmarks Tab gains a second view mode (list/run vs Inspect); state returns cleanly via Back.
+- HTML report Expansion Tree remains a summary; Inspect is the audit UX.
+- Earlier “no expected-answer compare panel” clause is superseded by the labeled side-by-side strip (not a diff engine).