feat(mcp): JSON-paste path in Add MCP server dialog

[pjdoland]

Summary

@mbektas asked for a paste-friendly alternative to the field-by-field form when adding an MCP server. The dialog now has Scope at the top, a Form/JSON tab control below it, and a JSON textarea that parses common copy-paste shapes into the same IClaudeMCPAddInput shape the form already emits.

Solution

Dialog layout. Scope is the first field. Below it, a WAI-ARIA tablist toggles between Form and JSON. The Form panel is the existing inputs; the JSON panel is a single textarea with a representative placeholder.

Paste parser (src/components/claude-mcp-paste.ts). Accepts:

• bare "server-key": { ... } (the shape that lands when you copy a single entry out of a .mcp.json)
• wrapped { "server-key": { ... } }
• full { "mcpServers": { "server-key": { ... } } }
• stray leading or trailing comma (copy-from-larger-config artefact)

Multi-server payloads, empty objects, non-object server values, and unparseable input are rejected with guiding error messages. configToInput translates a parsed entry into IClaudeMCPAddInput, inferring transport from the shape, but honors an explicit transport field when present and rejects mismatches (stdio with no command; sse/http with no url) rather than silently downgrading. Six-agent review flagged the silent-downgrade as a real footgun.

Helpers moved to a sibling module (claude-mcp-paste.ts) so the unit tests don't drag the React tree in to exercise pure data functions.

A11y. The Form/JSON control uses role="tablist" (not radiogroup, which doesn't fit a UI that swaps the rendered subtree). Arrow-Left / Arrow-Right move between tabs with roving tabindex. A useEffect focuses the right input when the user actively switches modes but skips the first run so it doesn't steal focus from the Scope select on initial mount.

Testing

pytest tests/ --ignore=tests/test_claude_client.py -q (709 passed). jlpm tsc --noEmit, jlpm lint:check, jlpm jest all green; new jest suite claude-mcp-paste.test.ts is 23 cases covering each paste shape, the empty / multi-server / non-object / array / primitive rejections, the explicit-transport-mismatch rejections (the footgun fix), and IClaudeMCPAddInput mapping (stringification of env values, http inference, sse override, unrecognized transport falls back to shape).

Manual: opened the dialog locally, confirmed Scope sits at the top, tab semantics work with keyboard, paste of the issue's example JSON populates correctly.

Risks / follow-ups

• The parser doesn't strip // comments. A future enhancement could pre-strip JSON-with-comments via a small regex pass, but the standard error message ("Invalid JSON: ...") is informative enough for now.
• The Form panel state is preserved when the user toggles to JSON and back. That's intentional: a user who mis-types JSON and wants to switch to Form to debug shouldn't lose their work.
• Skipped: a React Testing Library test for the dialog's mode-toggle wiring. The 23 unit tests pin the data layer; the UI wiring is a one-liner that I verified manually. Worth adding if regressions appear.

Closes #278

[mbektas]

thanks!