Address seed-packet review: 413 mapping, deadline, rollback, dedup

Gadfly findings on #94, the real ones:

- scanSeedPacket extends only the READ deadline; a slow upload + a live
  vision call runs past the server's absolute 30s WriteTimeout and the
  successful response is silently dropped (the #78 failure mode). Extend
  the write deadline too (scanWriteTimeout).
- An oversized upload tripping MaxBytesReader was mapped to 400; it's 413.
  Detect *http.MaxBytesError and report IMAGE_TOO_LARGE.
- Split imagenorm error mapping: ErrTooLarge->413, ErrUnsupported->400,
  genuine read/encode faults (and a failed file.Open)->500, not 400.
- CreateFromPacket discarded the plant it created when the lot then
  failed, contradicting its own doc. Roll the new plant back instead so
  the confirm is all-or-nothing (a fresh plant has no lots/plantings, so
  the delete is safe; log-and-continue on cleanup failure).
- Dedup: packetLotRequest and seedLotCreateRequest shared every lot
  field. Extract a seedLotFields base both use. validCategory now reuses
  plantCategories. EffectiveConfig resolves agent+vision from one
  settings-row read instead of two.
- capabilities swallowed an EffectiveVision error silently; log it.
- vision test hand-copied Extract's body (drift risk). Split generate()
  out of Extract so the hermetic test drives the real request builder.

Tests: rollback-on-lot-failure (service), oversized->413 (api).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

internal/api/seed_lots.go

@@ -16,9 +16,12 @@ import (
 // the buyer — a lot is never shared along with a garden — so every handler here
 // scopes to the session actor with no garden in the picture.
 
-// seedLotCreateRequest is the body for POST /seed-lots.
-type seedLotCreateRequest struct {
-	PlantID        int64    `json:"plantId" binding:"required"`
+// seedLotFields is the lot half of a create body — every field EXCEPT which plant
+// it attaches to. seedLotCreateRequest adds a required plantId; the seed-packet
+// confirm supplies none (the plant comes from its plantId/newPlant choice), so it
+// embeds these fields directly. Sharing one struct keeps the two request shapes —
+// and their validation — from drifting apart.
+type seedLotFields struct {
 	Vendor         string   `json:"vendor"`
 	SourceURL      string   `json:"sourceUrl"`
 	SKU            string   `json:"sku"`
@@ -32,15 +35,28 @@ type seedLotCreateRequest struct {
 	Notes          string   `json:"notes"`
 }
 
-func (r seedLotCreateRequest) toInput() service.SeedLotInput {
+// toInput builds the service input with no plant attribution; callers that know
+// the plant (the create handler; the packet confirm) set PlantID afterwards.
+func (f seedLotFields) toInput() service.SeedLotInput {
 	return service.SeedLotInput{
-		PlantID: r.PlantID, Vendor: r.Vendor, SourceURL: r.SourceURL, SKU: r.SKU,
-		LotCode: r.LotCode, PurchasedAt: r.PurchasedAt, PackedForYear: r.PackedForYear,
-		Quantity: r.Quantity, Unit: r.Unit, CostCents: r.CostCents,
-		GerminationPct: r.GerminationPct, Notes: r.Notes,
+		Vendor: f.Vendor, SourceURL: f.SourceURL, SKU: f.SKU, LotCode: f.LotCode,
+		PurchasedAt: f.PurchasedAt, PackedForYear: f.PackedForYear, Quantity: f.Quantity,
+		Unit: f.Unit, CostCents: f.CostCents, GerminationPct: f.GerminationPct, Notes: f.Notes,
 	}
 }
 
+// seedLotCreateRequest is the body for POST /seed-lots.
+type seedLotCreateRequest struct {
+	PlantID int64 `json:"plantId" binding:"required"`
+	seedLotFields
+}
+
+func (r seedLotCreateRequest) toInput() service.SeedLotInput {
+	in := r.seedLotFields.toInput()
+	in.PlantID = r.PlantID
+	return in
+}
+
 // seedLotUpdateRequest is the body for PATCH /seed-lots/:id: every field
 // optional, plus the required current version. The nullable columns are
 // json.RawMessage so an explicit null (clear it) is distinguishable from an