Fix viewer search and consolidate search routing, too

[eyeseast]

Closes #846 and consolidates routing logic around search.

For PDF pages, we're now getting the search query directly from the URL, instead of props, and reacting to URL changes.

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Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	30.81%	6699 / 21738
🔵	Statements	30.81%	6699 / 21738
🔵	Functions	49.63%	273 / 550
🔵	Branches	75.56%	1008 / 1334

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/lib/components/forms/Search.svelte	0%	0%	0%	0%	1-74
src/lib/components/viewer/PDFPage.svelte	0%	0%	0%	0%	1-253
src/lib/components/viewer/ReadingToolbar.svelte	0%	0%	0%	0%	1-140
src/lib/components/viewer/Text.svelte	0%	0%	0%	0%	1-40
src/lib/components/viewer/ViewerContext.svelte	0%	0%	0%	0%	1-193
src/lib/utils/search.ts	82.92%	75%	75%	82.92%	14-15, 76-80
src/routes/(app)/documents/[id]-[slug]/+page.svelte	0%	0%	0%	0%	1-66
src/routes/(app)/projects/+page.svelte	0%	0%	0%	0%	1-118
src/routes/embed/documents/[id]-[slug]/+page.ts	0%	0%	0%	0%	1

Generated in workflow #767 for commit 014fa79 by the Vitest Coverage Report Action

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[eyeseast]

Do we still need query and getQuery in ViewerContext? Right now they're only used by Text and ReaderToolbar and seem like they could be replaced by the utility.

We probably don't. I'll take them out.