docs: refresh markdown to v0.50.245 + add CONTRIBUTORS.md

- New CONTRIBUTORS.md: full ranked credit roll for all 66 contributors
  (5+ tiers), with first/latest release versions, single-PR roll, and
  attribution methodology. Generated from git log + gh pulls API +
  CHANGELOG mention parsing.

- README.md: stack-ranked top-10 contributors table at the top of the
  Contributors section, link to CONTRIBUTORS.md for the full list.
  Updated test count (1898 → 3309). Refreshed @franksong2702 and
  @bergeouss entries to reflect their broader bodies of work (now
  the #1 and #2 external contributors).

- ARCHITECTURE.md: removed stale 'tracks upstream v0.50.36' header;
  bumped current shipped build to v0.50.245 with current architecture
  state notes (streaming-markdown vendoring, byte-range streaming,
  configurable-model-badges).

- ROADMAP.md / SPRINTS.md / TESTING.md: header/last-updated bumps to
  v0.50.245 and 3309 tests. SPRINTS.md 'Where we are now' section
  refreshed for current CLI/Claude parity (~95% Claude parity now).

Generated by aggregating CHANGELOG attribution lines, gh PR API
authors, and CHANGELOG version-section walks. Internal/bot accounts
filtered out.

ARCHITECTURE.md

@@ -7,10 +7,10 @@
 >
 > Keep this document updated as architecture changes are made.
 
-> Current shipped build: `v0.50.36-local.1` (April 16, 2026).
-> Baseline: upstream `nesquena/hermes-webui` `v0.50.36`.
-> Intentional local delta: first-time password enablement from Settings immediately issues a `hermes_session` cookie so the current browser remains signed in. The previous `Assistant Reply Language` customization has been removed, legacy `assistant_language` settings are filtered out on load/save, the workspace panel closed/open state is preloaded via a `documentElement` dataset marker before `style.css` paints to avoid a first-load desktop flash, transcript disclosure cards now animate caret rotation and body expansion with transitionable `max-height`/`opacity` states instead of `display:none/block`, and thinking cards now share the same rounded bordered card chrome as tool cards while keeping their gold palette.
-> Automated coverage: 1353 tests collected (`pytest tests/ --collect-only -q`).
+> Current shipped build: `v0.50.245` (April 30, 2026).
+> Automated coverage: 3309 tests via `pytest tests/ --collect-only -q`. CI runs on Python 3.11, 3.12, and 3.13 against every PR.
+>
+> Notable architecture state as of v0.50.245: workspace panel closed/open state is preloaded via a `documentElement` dataset marker before `style.css` paints to avoid first-load flash; transcript disclosure cards animate via transitionable `max-height`/`opacity` states; thinking cards share rounded bordered card chrome with tool cards (gold palette); incremental streaming-markdown via vendored `streaming-markdown@0.2.15` (no CDN); HTTP byte-range streaming for large media; SSE-driven session sidebar with `pending_user_message` + `active_stream_id` lifecycle tracking; configurable model badges (`primary` / `fallback N`) computed in `_build_configured_model_badges()` and provider-aware in the dropdown picker.
 
 ---
 
@@ -33,11 +33,6 @@ frontend framework. The Python server is split into a routing shell (server.py)
 business logic modules (api/). The frontend is seven vanilla JS modules loaded from static/.
 This makes the code easy to modify from a terminal or by an agent.
 
-For the current local build, the codebase is intentionally as close to upstream as possible:
-the app now tracks upstream `v0.50.36`, keeps the password-session continuity patch in the
-settings/onboarding flow, and does not carry forward the prior reply-language preference
-feature.
-
 Hermes-level chrome is intentionally consolidated: the sidebar has no dedicated brand header.
 Instead, the footer exposes a single "Hermes WebUI" launch button that opens one tabbed
 control-center modal for global preferences, conversation import/export, and clear-conversation