feat(lifeboard): packs, recipes and the shopping-list arithmetic

[ivanmkc]

The stack

#	PR	What it adds	Tests at this point
1	#311	A real localStorage for the test suite on Node 25	viewer 747
2	#312	@ivanmkc/termchart-canvas; injectable interact transport	canvas 473 · viewer 278
3	#313	lifeboard PWA: fact log, boards, service worker	lifeboard 36
4	#314	Shell, family profiles, tap layer	lifeboard 82
5	#315	The agent turn, four providers, Connections	lifeboard 142
6	#316	Packs, recipes, shopping-list arithmetic	lifeboard 231
7	#317	Provenance and lineage	lifeboard 257
8	#318	Calendar, Gmail, mail triage	lifeboard 301
9	#319	The bridge and long jobs	cli 314 · lifeboard 320
10	#310	Proactivity, scheduled boards, Google sign-in	cli 320 · lifeboard 343
11	#320	Persistence audit fixes: multi-tab, stale builds, no-storage boot	lifeboard 350
12	#321	User guide, bridge setup, QA guide, persistence audit	lifeboard 350
13	#322	A plan for third-party integrations (docs only)	unchanged
14	#323	A practice drill a board can define: audio + Q&A	canvas 485 · lifeboard 372
15	#325	Export and restore	lifeboard 389
16	#326	Draft a message, approve it, then send	lifeboard 399
17	#327	Hand long work to the Mac	lifeboard 406
18	#328	A Packs screen, and authoring one by describing it	lifeboard 418
19	#329	Activity — what changed, who changed it, undo	lifeboard 428
20	#330	Four defects found reviewing the stack	cli 323 · lifeboard 431

Every branch in the stack was checked out on its own and verified independently: npm install, tsc --noEmit for every package, npm test across the workspace, and the offline e2e where it exists. All twenty are green — no branch depends on a later one to build or pass. Full viewer e2e (11 suites, 106 assertions) was run on #312 as the behaviour-preservation evidence for the extraction.

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Stack position: 6 of 10. Base: lifeboard/04-agent.

Packs — recurring operations as data — and recipes as the first consumer.

Packs are data, never code. A pack names a capability and a view builder; the app owns both and looks them up in a table. Installing one can never introduce behaviour the app did not already have. Validation is the security boundary and is written as one: allow-lists throughout, https-only feeds, a refresh floor of 30 seconds, and a declared writes set enforced at the point of application rather than trusted in each capability.

Selection caps at two packs per turn. Each adds a few hundred tokens of instructions, and a prompt carrying six answers worse than one carrying the right one.

The arithmetic is code, and this is where every competitor is visibly wrong. An item's quantity is the sum of its contributions, one per recipe, so re-scaling pancakes from 6 servings to 4 updates that recipe's share of a line already on the list instead of adding a second flour. Amounts that cannot honestly be summed — 100 g butter plus 1 cup butter, or "a handful" — are shown as the part we know plus "+ more", never as an invented total. Ranges take the top: running out is worse than a spare onion.

Nothing is ever silently removed. Pantry staples are marked and left on the list to tick; taking a recipe back off leaves its lines with a note rather than deleting them. Plan to Eat shipped the opposite and withdrew it.

Instacart's schema is adopted rather than hand-rolled — name separate from display_text, the measurements array rather than the deprecated flat pair. The call is written and injectable but off without a key, which this app has nowhere to keep; the floor that always works is a prefilled search per item. Amazon's legacy add-to-cart URL is deliberately unused: it is not a contractual API.

A bound board is authored once and re-rendered from data forever after — no model on a timer. A failed refresh keeps the last good data behind a visible stale marker instead of blanking, and probeSource runs at authoring time so "your browser cannot read this feed" is said while the board is being made.

Verified: 231 unit tests, including the 6→4 re-scale, the staples rule, and a pack that declares an undeclared write being refused.

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