Customizing the CV in the browser: the URL holds what is hidden, a stylesheet hides it

Decides #38, which ADR 0012 deferred. Stays within ADR 0003: no entifix in the browser.

Context

A variant is one person's guess at what a reader wants. The visitor holding the job description knows better: leave out a section, an old position, a technology the role does not care about, then print. Every sheet is rendered at build time, and the page must stay that way: the static HTML, the prebuilt PDFs and the ATS pages are what search engines, parsers and phones get.

Decision

• The server renders everything; a stylesheet hides. On the human sheet, each section, position and technology carries data-cv-part (section:education, position:<period id>, tech:<technology id>). A hidden part is one display: none rule in a single <style id="cv-hidden"> in <head>. The markup never changes per visitor, so hydration never mismatches, and the rule holds in print, so printing honours every choice.
• The URL holds the choices: ?hide=section:education,tech:react. A customized sheet is a link, and reloads the same. Tokens are checked against ^(section|position|tech):[a-z0-9-]+$, so none can break out of its selector; a token naming a part the sheet does not have matches nothing. The customizer reads the URL through useSyncExternalStore and rewrites it with history.replaceState, as the radar's filter does (ADR 0014).
• Hidden before the first paint. An inline script ahead of the sheet reads ?hide= and writes the stylesheet, as ThemeScript sets the palette. A shared link opens without a flash of what it hides. After hydration the customizer owns the stylesheet, and removes it when its page is left: on a client-side navigation the inline script does not run again.
• The controls are plain props. Sections, positions and technologies reach the client component as { part, label } lists built at build time; no entifix code reaches the page, and e2e checks the CV's scripts for it as it does the radar's.
• Human sheet only. The ATS pages carry no parts, no script and no controls: what a parser reads stays exactly what was built.
• The prebuilt PDF stays whole. It cannot know a visitor's choices. When anything is hidden the customizer says so: the download is the full sheet, printing keeps the choices.
• Switching reading or mode starts afresh. Those links are built without the query: positions and technologies differ between variants, and the ATS sheet has no choices to keep.

Consequences

• The CV page ships a client island. Its scripts are held to a budget in budget.spec.ts: 159.6 KB measured, 170 KB allowed.
• Hiding only removes content, so a customized sheet still fits one A4 page (ADR 0012) without a check of its own.
• A browser without scripting gets the full sheet and no controls: the same page as before #38.
• The human sheet's visual baselines include the closed "Customize" disclosure.

Alternatives considered

• State only in the page: nothing to parse, nothing to flash, but a choice is lost on reload and cannot be shared.
• Re-rendering the sheet on the client from its data: puts the sheet's logic in the browser, and hydrating a sheet that differs from its HTML is a mismatch to manage. CSS over the built markup needs neither.
• Hiding with a class set by React on each part: the parts are server components, and would have to become client ones.