Salvages PR #28832 onto current main plus a small follow-up so the new slashed plugin routes actually work end-to-end.

What's in this PR

Commit 1 — refactor(web): dashboard typography & contrast pass (Austin Pickett, squashed)

Squashes all 19 commits from #28832. Original authorship preserved via --author=.

• Removes the global uppercase + font-mondwest from the App.tsx root.
• Introduces text-display from @nous-research/ui@0.16.0 on intentional brand chrome (page titles, sidebar headings, segmented filters) so the brand-uppercase look is opt-in per element rather than global.
• Replaces stacked-alpha text colors (text-muted-foreground/60, opacity-30 on nav headers, etc.) with semantic text tokens (text-text-primary/secondary/tertiary/disabled) so contrast stays WCAG-AA across all 7 built-in themes.
• Raises every sub-12px arbitrary text size to text-xs where it was actual content.
• Maps --color-muted-foreground → --color-text-secondary in index.css so existing call sites land on the new contrast floor without per-file changes.
• Bumps @nous-research/ui 0.14.0 → 0.16.0, regenerates web/package-lock.json, refreshes nix/web.nix fetchNpmDeps hash.
• New "Typography & contrast rules" section in web/README.md.

Beyond the original typography pass, the PR also picked up:

• hermes_cli/web_server.py — widens the 5 dashboard plugin routes to {name:path} and relaxes _validate_plugin_name (still rejects .. and \, strips leading/trailing /, allows internal /). Enables enable/disable on category-namespaced plugin keys like observability/langfuse and image_gen/openai that the FE was encodeURIComponent-ing.
• web/src/lib/api.ts — adds a pluginPath() helper that preserves / segments when building the URL.
• Sessions / Env / Keys page chrome polish and two new i18n keys (overview, showMore/showLess) across all 18 locales.

Commit 2 — fix(plugins): widen _sanitize_plugin_name for category-namespaced names

The dashboard plugin routes in commit 1 accept slashed names, but _sanitize_plugin_name (the deeper guard used by update/remove on installed plugins) still rejected forward slash. So dashboard update/remove on a slashed plugin returned "not found" even though the directory existed.

• Adds an opt-in allow_subdir=True flag that permits internal / and strips leading/trailing /, while still rejecting .. and \ and still asserting the resolved target lives inside plugins_dir.
• Opted in at the two read-paths that operate on installed plugins (_require_installed_plugin for CLI update/remove, _user_installed_plugin_dir for the dashboard equivalents).
• Install path keeps the default allow_subdir=False — freshly cloned plugins always land top-level under ~/.hermes/plugins/<name>/.
• 6 new unit tests covering the new flag's allow/reject matrix.

Validation

• scripts/run_tests.sh tests/hermes_cli/test_plugins_cmd.py — 71/71 passed (65 existing + 6 new).
• E2E with an isolated HERMES_HOME and a real ~/.hermes/plugins/observability/langfuse/ checkout:
  • _sanitize_plugin_name(..., allow_subdir=True) resolves slashed name to the correct path.
  • Install path (allow_subdir=False) still rejects slash.
  • _user_installed_plugin_dir("observability/langfuse") returns the dir; dashboard_remove_user_plugin("observability/langfuse") succeeds and removes the directory.
  • .., \\, foo/../../etc all still rejected with allow_subdir=True.
  • Leading slash stripped; resolved target stays inside plugins_dir.

Closes

Closes #28832 (squash-merged here with Austin's authorship preserved on commit 1).

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