[ntindle]

Lids for bins (F16): flat cover lid for every placed bin STL

Bin options gains a "Lids for bins" switch. When on, every placed bin gains a
flat 3 mm cover lid as its own STL in the Download files zip: one lid per
distinct bin footprint, shared across heights, counted in the Print plan
card and in the print estimates, with its own 3MF lid plates. The lid sits
on the stacking lip; it has no snap lip, hinge, or handle. Persisted as
gridfinity_lids, local-only, not in share links (same precedent as
labelTabs, dividers, and testFit).

Geometry

• Lid mesh: a flat box spanning the bin outer footprint
  (binOuterSize, the same dims the bin part itself uses), 3 mm thick
  (LID_THICKNESS_MM). 12 triangles, bounds exactly
  [0, 0, 0]–[width, depth, 3], signed volume exactly width × depth × 3.
• Lid/tab interplay: the label tab protrudes 1.2 mm past the bin's front
  face, outside the lid footprint (they touch only at the front plane), so
  a lid laid on the stacking lip sits flat and does not intersect a tab,
  and the tab still rises above the lid. Lids are separate STLs, not merged
  into bin meshes, so tabs and dividers are undisturbed.
• Lid/height: lids are keyed by footprint only (lid:<cellSize>:<w>x<d>),
  so the same footprint at different heights shares one lid with summed
  counts. Skipped bins get no lid; counts multiply by the drawer count.
  Half-grid lids stay distinct (half-grid qualifier in key, stem, label).

Wiring

• useGridfinitySettings adds gridfinity_lids (new key only, default
  false; legacy migration untouched). GridfinityCalculator drills lids
  to BinOptions, DownloadButton (→ createPrintFiles), and
  PrintPlanCard (→ collectPrintParts → part rows + estimatePrint).
• exportFiles routes lids to their own 3mf/plate-N-lids.3mf plates
  (never mixed into bin/baseplate plates) and adds the README lid note
  plus the lid size line. Test-fit logic is untouched (baseplate/spacer
  stems only). Share format untouched (shareLayout.ts not modified).

Tests (repo config: vitest --config vite.config.test.js)

• Full suite: 52 files, 616 passed / 11 skipped (was 603 passed; +13 new).
• New: lidMesh bounds/volume/triangle-count/rejection (5),
  printParts lid grouping/counts/skipped/multi-drawer (4),
  printEstimates lid volume == lid mesh volume (1), exportFiles lid
  STL + lid 3MF plate + README note/line (1), BinOptions switch (1),
  PrintPlanCard lid row on/off (1).
• Lint clean (--max-warnings 0), tsc --noEmit clean, build green
  (index chunk 237,001 → 237,798 B, +0.3%; lazy export chunk
  22,830 → 23,535 B, +3.1%).

Perf vs trunk (same box/day, local preview, node scripts/measure.mjs --n=15 --lh=3, two pairs)

Metric	Branch	Trunk
Parity	51.0% (23 ✅ + 5 🟡 / 50)	50.0%
Lighthouse perf	68 / 77	77 / 72
TTI	3958 / 3479 ms	3514 / 3724 ms
Input-to-preview (median)	41.9 / 32.7 ms	40.2 / 186.5 ms
Layout task	4 steps, 490 / 503 ms	4 steps, 496 / 795 ms
Share task	1 click, 83 / 79 ms	1 click, 117 / 73 ms

Verdict: no credible regression. Pair 1's load gap did not reproduce in
the reversed-order pair; within-side swings exceed any branch-trunk gap.
Pair 2's trunk interaction outliers (186.5 / 795 ms) ran while the
reviewer's test run shared the box, and they favor the branch anyway.
The diff touches no measured code path.

Live verification (Lane B — run on the deploy preview)

Core tasks 1–3, plus the lids feature, exact steps:

1. Default layout (15×12 in, Bambu Lab A1): results + preview render.
2. Half-size toggle on → finer grid, off → restored exactly.
3. Download files + Share link + Bin labels + Print plan present.
4. Find the "Lids for bins" switch with the description "Every printed
   bin gets a flat 3 mm cover lid that sits on the stacking lip. Lids
   have no snap lip, hinge, or handle." Confirm OFF persists across
   reload.
5. Place a bin (drag-draw, e.g. Bin 4 × 3 · 3u). Read the estimate line
   with lids OFF, then turn lids ON: the estimate must increase by
   exactly the lid volume — footprint × 3 mm per lid (for a 4 × 3 bin:
   167.5 × 125.5 × 3 = 63,064 mm³ → about +2 h 11 min, +78 g PLA,
   +$1.56 at the default PLA/$20/kg/~8 mm³/s assumptions, for one bin
   in one drawer). Confirm ON persists across reload.
6. Confirm the Print plan card gains a lid row and the bin plate rows are
   otherwise unchanged, and Download files reports the lid STL in the
   toast (e.g. lid-4x3-x1.stl).

Trunk expectations: everything above except step 4–6 (no lids switch,
no lid STL, no lid row); the estimate line must not change when the
switch is absent.

Review trail

• Independent review of the code commit: code SHIP-ready; one docs-only
  blocker (missing scoreboard entry), fixed by a docs-only amend.
• Docs-delta re-review: SHIP IT on the amend (scoreboard numbers match
  all four perf JSONs; feature-map line 12 corrected). One reviewer
  wording nit (Lighthouse "wider" phrasing) fixed with a docs-only prose
  amend after the verdict; no numbers changed.
• Feature map: F16 ❌→🟡 (flat cover only, limits stated); F15 clause
  updated ("separate flat cover lids; no scoops or magnets yet").
  Parity 50.0% → 51.0%.
• Still open (not this PR): snap lip / hinge / handle lids; configurable
  divider counts and positions; half-grid lid stem distinctness test
  (behavior verified by construction, no dedicated test yet).

[netlify]

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[github-actions]

PR Quality Report 📊

Check	Status
TypeScript	✅
ESLint	✅
Tests	✅
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[codecov]

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✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
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=======================================
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  Branches        ?     1076           
=======================================
  Hits            ?     3465           
  Misses          ?      198           
  Partials        ?       21           

Flag	Coverage Δ
unittests	94.05% <100.00%> (?)

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[ntindle]

Lane B PASS on the deploy preview (https://deploy-preview-160--gridfinity-drawer-planner.netlify.app, head be5e979) — all 8 steps, no page errors:

• Core tasks: 15x12 + Bambu Lab A1 -> "4 baseplates · 5 spacers", preview rendered; half-size on -> finer 12x12 grid, off -> restored exactly; Download files + Share link + Bin labels + Print plan present.
• "Lids for bins" switch found with the exact description text; OFF persists across reload.
• Placed "Bin 4 x 3 · 3u"; estimate OFF exactly "~8 h 59 min · ~321 g PLA · ~$6.42" -> ON exactly "~11 h 11 min · ~399 g PLA · ~$7.98" (+78 g, +$1.56 — exactly the 167.5 x 125.5 x 3 = 63,064 mm3 lid volume; the displayed time delta of +2 h 12 min vs the lid-only +2 h 11 min 23 s is rounding of the two totals to whole minutes, not a volume error).
• ON persists across reload; Print plan shows "1x Lid 4 x 3" with bin plate rows otherwise unchanged.
• Download toast: "Downloaded gridfinity-15x12in.zip 11 parts as STL files and 4 prints as 3MF plates" (10 parts without lids -> 11 with lids).
• Independently confirmed from the downloaded zip: stl/lid-4x3-x1.stl present, 3mf/plate-4-lids.3mf present, README lid line "167.5 x 125.5 x 3 mm".

Merge gates: CI 31/31 green, perf no-regression (two pairs), independent review SHIP IT + docs-delta SHIP IT, scoreboard updated, RUNLOG trail present. No claude-review check on this head (no exception needed).