Release 1.19.0: request reliability, editor, and environment UX

[snj07]

Summary

ReqLab 1.19.0 improves correctness in request execution and copying, adds a desktop-quality Environment editor, expands editor productivity, and refreshes the MCP/product documentation.

Highlights

• Preserve repeated query parameters and headers, with consistent URL encoding for Send and Copy.
• Send normal GraphQL editor content in the correct GraphQL envelope.
• Support API-key placement in headers or query parameters, including Postman import/export.
• Persist disabled, repeated, and secret request rows reliably across save, reopen, duplication, and autosave.
• Add a resizable, searchable Environment editor with persisted dimensions.
• Add editor find/replace, go-to-line, line operations, bracket matching, indent guides, and optional line/column status.
• Refresh README, MCP documentation, sample requests, and screenshots.
• Publish curated 1.19.0 changelog notes with the GitHub Release.

Compatibility

Existing collections and tabs remain compatible. New persistence fields are additive, and existing API keys continue to default to header placement.

Related issues

Closes #6
Closes #7
Closes #8
Closes #14