Document the supported-browser matrix (browsers, ClickHouse versions, IdP requirements)

[BorisTyshkevich]

Part of #68 (Roadmap to 1.0.0) — release-blocker.

Problem

The README never states which browsers/versions are supported, nor the supported ClickHouse versions or IdP requirements. A 1.0 cannot ship silent on this — especially given the html{zoom} reliance (see the zoom de-risk + WebKit-e2e issues), which makes the supported-engine set a real, non-obvious constraint.

Ask

Add a concise support matrix / system-requirements section to the README:

• Browsers + minimum versions (desktop Chrome/Edge/Firefox; Safari status pending the WebKit decision). Note desktop-only if that's the call (no responsive CSS today).
• ClickHouse server versions (incl. Antalya vs OSS + JWT-verify sidecar notes).
• IdP/OAuth requirements (PKCE public client preferred; the client_secret caveat → link SECURITY.md).

Acceptance

• README has a clear, scannable support matrix.
• Browser row reflects the WebKit/Safari decision from the related issues.

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Folded in from the roadmap (#68) nice-to-haves:

• State the desktop-only stance explicitly — there is no responsive CSS today (no @media, fixed px, overflow:hidden on html/body). The matrix should say "desktop browsers" (or add a minimal narrow-viewport fallback) so a phone/tablet user isn't surprised by a silently-broken layout.

[BorisTyshkevich]

Browser-row input from #69 (now implemented; PR open):

Decision: desktop Safari (WebKit) is supported. The Playwright e2e suite was extended to a third engine (webkit) and runs on every CI push/PR alongside Chromium and Firefox. The full suite — editor highlight/selection alignment (the html{zoom} × scrollbar-shrink math), the schema-double-click execCommand insertion path, the schema-lineage graph, and the EXPLAIN-pipeline pan/zoom — passed on WebKit: 36 passed across the three engines (CI run). So the html{zoom}-based layout does not diverge on WebKit for the surfaces under test.

Browser row for the matrix here:

Browser	Status	Notes
Chrome / Edge (Chromium)	✅ Supported	primary
Firefox	✅ Supported	execCommand insertion path e2e-guarded
Safari (WebKit)	✅ Supported	e2e-verified green on CI; html{zoom} layout holds
Mobile / narrow viewport	❌ Not supported (today)	no responsive CSS (fixed px, overflow:hidden); desktop-only — formal stance is for this issue to set

README now carries a concise Supported browsers section pointing here for the full matrix (browser min-versions + ClickHouse versions + IdP requirements).

[BorisTyshkevich]

Finding from #70 (PR #92) — relevant to the browser matrix.

Real Safari and Playwright's bundled WebKit diverge on how CSS zoom interacts with getBoundingClientRect / viewport units:

• Real Safari: getBoundingClientRect stays in CSS px (rect/offsetWidth ratio = 1), and vw/vh track zoom (100vh == one screen).
• Playwright WebKit (and Chromium): getBoundingClientRect is post-zoom (ratio = --zoom), and vw/vh ignore zoom (100vh overshoots by the zoom factor).

Consequence for this matrix:

1. The pointer/caret/drag math self-calibrates to the live rect ratio, so it's correct on both — no per-engine caveat there.
2. The fullscreen graph panels needed a runtime-measured --vp-zoom divisor (1.2 Chromium / 1.0 Safari) — fixed in fix(zoom): correctly size fullscreen graph panels on Safari under html{zoom} (#70) #92.
3. CI's WebKit is not a faithful Safari proxy for zoom×rect/viewport behaviour. Add WebKit/Safari to e2e + decide the supported-browser stance #69/test(e2e): add WebKit/Safari to the Playwright matrix + decide the support stance (#69) #90's "Safari verified on CI" did not actually exercise this path; the real-Safari viewport-unit behaviour was caught and verified manually. The matrix should note that real-Safari layout under html{zoom} requires manual verification (or a real-Safari runner) until the zoom dependency is removed (folded into Consider CodeMirror 6 for the SQL editor (schema-aware autocomplete) #21/Schema graph: multi-select + group-move of nodes (marquee, Shift-click, ⌘A) with single-step undo #66 per Roadmap to 1.0.0 #68).