[AZ-484] Cycle 1 Step 17 Retrospective: report + structural snapshot

Closes the AZ-484 cycle:
- retro_2026-05-11.md: 5 patterns identified (code-review-PASS does
  not imply runtime PASS; spec-authorship under-specifies wire
  format / test sites; NFR test-spec entries decoupled from runner
  scripts; pre-existing module doc staleness; pre-existing security
  Mediums now visible). Top-3 actions ranked by impact, with target
  rule/skill files and owners.
- structure_2026-05-11.md: baseline structural snapshot for future
  retro deltas (6 components, 12 ProjectReference edges, 0 cycles
  in import graph, 0 net architecture violations, 1 frozen
  contract, ~14% contract coverage).
- LESSONS.md: header rewritten to describe the two-layer format
  (deep lessons + 15-entry ring buffer); appended 3 new ring-buffer
  entries (testing/process/estimation) sourced from this retro.
- _autodev_state.md: cycle 2 starting at Step 9 New Task.

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

_docs/LESSONS.md

@@ -2,6 +2,13 @@
 
 Recurring bugs, surprising library behaviors, and process insights extracted from completed cycles. Newest at the top. Keep entries short — this is for fast scanning at the start of new cycles, not exhaustive history.
 
+This file has two layers:
+
+- **Deep engineering lessons** (L-NNN): library bugs, architectural insights, multi-paragraph context. Persist forever.
+- **Ring buffer** at the bottom: most recent 15 single-sentence lessons emitted by the retrospective skill, consumed by `new-task` / `plan` / `decompose` / `autodev` Step 0. Oldest entries drop off the top.
+
+Categories: `estimation` · `architecture` · `testing` · `dependencies` · `tooling` · `process`
+
 ---
 
 ## L-001 — Dapper `TypeHandler<T>` is bypassed for enum types during read deserialization
@@ -27,3 +34,12 @@ If the enum's wire string happens to match a member name case-insensitively (e.g
 - If you must keep an enum-typed field, write at minimum one integration test that reads the enum back through Dapper from a real database row.
 
 ---
+
+## Ring buffer (last 15 entries — newest at top)
+
+- [2026-05-11] [testing] Persisted enums need a Dapper read-roundtrip integration test — unit-testing the type handler in isolation does not prove read-side behavior (see L-001).
+  Source: _docs/06_metrics/retro_2026-05-11.md
+- [2026-05-11] [process] NFR test-spec additions must include the runner-script implementation in the same step, or be tagged "Deferred — harness work tracked in <ticket>"; otherwise scenarios accumulate as Unverified across cycles.
+  Source: _docs/06_metrics/retro_2026-05-11.md
+- [2026-05-11] [estimation] Task-spec test-site-count estimates must be backed by an explicit grep evidence block, not pattern-matched against neighboring code (AZ-484 spec said ~3 sites in `RegionServiceTests`; actual = 0).
+  Source: _docs/06_metrics/retro_2026-05-11.md