feat(#427): put the depth vocabulary on the DaisyUI primitives

[TortoiseWolfe]

Puts the depth vocabulary on the DaisyUI base classes so the remaining page tickets are composition work, not re-shadowing.

Why this comes first

The refresh was scoped to the six surfaces the comp drew. Measured across the app: 43 routes, 5 carrying any depth token, 38 never touched (#426). Those 38 are thin shells — /profile is 40 lines, /payment 31 — over 46 shared components built from ten DaisyUI primitives:

primitive	files		primitive	files
btn	106		badge	52
alert	88		textarea	37
input	78		modal	30
select	69		stat	29
card	60		table	19

Going route-by-route would hand-restyle the same button 106 times. This moves the whole app at once.

What changed

Two blocks of literal-black drop shadow are replaced. They existed so unmigrated pages still looked deliberate, and their own comment set the exit condition — "Remove this block entirely once every surface is on the depth tokens" — assuming migration meant hand-applying sh-plate everywhere. It doesn't have to.

treatment	applied to
plate (raised)	.card .alert .modal-box .btn
well (cut)	.stats
groove (channel)	.input .select .textarea .file-input .table thead th · .btn:active

Literal black is also what --sh-ink-shadow exists to replace: it derives from the theme's own surface, so it stays correct on both house themes rather than being tuned for the dark one and tolerated on the light.

Verified in a browser, not assumed

• .card → oklch(0.0959 0.038 282.93 / .55) on scripthammer-dark, oklch(0.4022 0.009 67.72 / .55) on scripthammer-light — each derived from that theme's base-100.
• retro is untouched, keeping its own DaisyUI shadow. The 32-stock-theme contract holds.
• 5 solid buttons take the plate; all 45 .btn-ghost on the home page take none. Ghost and link are flat by definition — shadowing them would make a quiet action read as a raised one.
• Focus rings survive. DaisyUI draws focus with outline: 2px solid, not box-shadow (components/input.css), so no rule here can erase it. Measured outlineWidth=2px outlineStyle=solid on a focused .input. This was the main a11y risk and it was checked before writing the CSS, not after.

The first probe of .btn returned none and looked like a failure — it had resolved querySelector('.btn') to a btn-ghost btn-circle in the nav, which is the excluded case. Re-probed against a non-ghost button.

Deliberately excluded

.badge — a ~20px pill with an inset shadow reads as mud at that size. Badges carry meaning through colour here, not depth. Called out so this reads as a decision rather than nine of ten.

The :not() chain is load-bearing

These selectors are [data-theme] .class — specificity 0,2,0 — while a Tailwind @utility is 0,1,0. Without the opt-out chain this block beats sh-plate/sh-well/sh-groove and an element carrying a depth utility silently renders its primitive's default instead. That exact failure is #379. Any rule added here needs the same chain.

Found while verifying this

#436 — form fields sit beside or below their label depending on the length of the label text. On /contact the four fields have byte-identical markup; .label is inline-flex, so the input wraps below only when labelWidth + inputWidth > containerWidth. "Subject" (59px) fits beside its input at 379 against a 384px container and lands one label-width off the grid. Predicts sharesLine in 4 of 4 fields. className="label" appears 32 times across 14 files. Not caused by this PR, and not fixed here.

Closes #427.