Copilot round 2 (suppressed comments). Five of the seven findings were the
accessibility of the new row list and one stray cast; all are addressed here.
- The reserved-key reason is now the key input's `error` **string** rather than
a bare boolean plus free-standing text. Mantine renders it in the input's own
error slot and wires the `aria-describedby` association, so a screen reader
learns *why* the field is invalid; a boolean only set `aria-invalid`. This
also deletes the duplicate `ReservedParamError` text and its Stack wrapper.
- Each control carries a per-row `aria-label` — the section heading and the
placeholders are not programmatically associated with the inputs, so the key
box, the value box, and a remove button announcing only "X" were
indistinguishable to assistive technology. The label names the row by its key,
falling back to "row N" while the key is still blank.
- Dropped an unnecessary `as unknown as Record<string, unknown>` in the
servers-route integration test: `MCPConfig.mcpServers` is already typed as
`Record<string, StoredMCPServer>`, so the entry's `oauth` reads directly.
Three tests cover the new behavior (accessible names, the blank-key row-number
fallback, and the aria-describedby association), each verified to fail against
the pre-fix component. No change to the reserved-key rule or the EMA boundary.
Signed-off-by: cliffhall <cliff@futurescale.com>