Comparison page refresh and a "deliberately not planned" section #69

Why

docs/comparison.md is the page reviewers quote, and it is honest today. As the parity issues land (multipart, cookies, client certs, digest, PKCE, Postman import, HTML report) its table and its "What apic does not do" list go stale one row at a time. It also lacks a clear statement of what will never be added and why, so the same requests keep coming.

What

• Add a row-level checklist to this issue and tick rows as the parity issues merge; each parity PR updates its row (add that to the PR checklist in CONTRIBUTING.md).
• Add Kulala.nvim and ijhttp columns, since both are .http runners people compare against.
• New section "Deliberately not planned": scripting and response handlers, custom step definitions, gRPC, WebSocket, MQTT/AMQP, a GUI beyond the terminal UI and the VS Code extension, a hosted workspace. One sentence of reason each, reusing docs/faq.md's wording, and a pointer to the escape hatches.
• Link the parity epics from the page so readers can see what is coming.

Where

docs/comparison.md, docs/faq.md, CONTRIBUTING.md.

Tests

Docs build and link check.