feat(ui): deliver a compact validator directory with explicit key comparison

[JSONbored]

Parent epic: #12012
Workstream: #12022
Related presentation scope: #11976; existing PR #11981

The validator directory puts secondary analysis ahead of the records and exposes quantities whose underlying token and entity scopes need further work. Deliver the independent directory cleanup now while canonical valuation, holdings and historical metrics remain tracked in #12014–#12021 and #11976.

Scope

Reuse PR #11981 and the current paper, graphite and mint design tokens. Put a compact summary, search and the operator table first. Keep observed identity, hotkey counts, take coverage and memberships clear; let readers expand a row and choose the exact keys they want to compare. Preserve supported URL state, complete exports and crawlable detail links.

Acceptance criteria

• Directory rows appear before secondary analysis, with a compact summary and consistent table controls.
• Stable operator IDs remain the row identity. Default ordering and visible/exported columns do not imply an unsupported financial ranking.
• Partial take coverage is explained in the table and CSV. Unknown values and original observation timestamps remain intact.
• Unsupported saved balance filters have an explicit, clearable notice; supported search, identity filters, sort and order survive reload and reset pagination correctly.
• Expanded rows expose exact hotkey links and explicit comparison selection without substituting an unchosen key. Up to three selected keys remain identifiable and the comparison action remains reachable on phones.
• Phone and tablet controls are usable by keyboard and touch; long keys, expanded content and comparison controls stay within their container. Phone rows use document scrolling.
• Column customization preserves valid interactive markup and separate disclosure/link keyboard behavior. Existing detail links and bounded server-rendered payload remain intact.
• Before/after captures cover 375/768/1280 in light and dark themes, including expanded rows and mobile filters; an interaction recording and relevant unit/browser checks are attached.
• Exact-head CI, merged source, deployed version and bounded public verification are recorded separately.

Scope retained elsewhere

This focused delivery does not close #11976 or #12022. Canonical stake distribution, valuation, returns, holdings and their visual profiles remain dependent on verified ingestion and contracts. No unavailable field is restored merely to fill a table or chart.

Delivery: PR #11981 merged as a19c4ce7453d37a39b5f887ca0ff0fb2eff866a7 after green CI. Cloudflare UI build 8c3cee82-8f55-473f-b1a4-fe286807cf53 succeeded; version 541fc786-77c4-4baf-82f8-7fd8048de039 serves 100%. Ordinary GET of /validators returned 200 with the new filter/directory markup and without the old concentration/total-stake panels. Local validation: 2,411 UI tests, 634 browser cases and the three-width/two-theme visual matrix in the PR.

[linear-code]

JSO-8766