docs: add the UI Capture and capture loss guides; state arm64's 6.4 kernel floor

[slayerjain]

Two changes, one commit each.

1. UI Capture guide

A new page, UI Testing → UI Capture (versioned_docs/version-4.0.0/running-keploy/ui-capture.md), covering:

• how to set up UI capture three ways: from the dashboard (with screenshots), over the REST API (curl), and from an AI agent through the Keploy MCP server;
• installing the SDK, its options, and what it records and masks;
• the capture states and what to do in each;
• reading flows, and what an agent's view of a flow leaves out;
• limitations and troubleshooting.

Why: a customer asked how to create the ui:ingest key the capture SDK needs. Nothing documented it, and until now nothing in the product let them do it.

Accuracy:

• Every request, response, field, state, permission, SDK option and limit on the page comes from the shipped code or a run against it. The REST examples are real responses from a local deployment, with keys and IDs replaced.
• The screenshots come from the real end-to-end test of this flow (enterprise-ui tests/projects/ui-testing/ui-capture-e2e.spec.ts, docs mode). They were taken on a local deployment, which the page says.

2. Capture loss warnings guide, and arm64's 6.4 kernel floor

A new page, Capture loss warnings (running-keploy/capture-loss.md), for the warning Keploy's eBPF capture logs when an app moves bytes without copying them through its own memory: --low-latency, a Sidecar with low_latency_mode, and the DaemonSet.

• It quotes the warning, the periodic report and the two startup warnings after which some losses go unmarked, and explains every field.
• A table maps the warning's words to a section per cause: sendfile, splice into and out of a socket, io_uring registered buffers, MSG_TRUNC, and a page the hook could not read. Each section gives the setting that avoids it (nginx, Apache, Tomcat, gunicorn, aiohttp, HAProxy, Java, Go).
• Each section has an explicit heading ID ({#sendfile}, …). The agent's docs field links to them (keploy/enterprise#2636), so keep these IDs when the page is edited or the next docs version is cut.
• The troubleshooting guide gets an entry pointing to it.

Every quoted line, field and level is checked against the agent's code, and every Go claim against the Go 1.27 standard library.

It also fixes a gap that affects users: that capture needs eBPF hooks arm64 kernels support only from 6.4 (x86-64 from 5.10). The platform requirements said 5.10 for everything, and the Kubernetes quickstart said nothing, so an arm64 node on Amazon Linux 2's 5.10 or AL2023's 6.1 looked supported. Both pages now say so, and what to use there instead; the quickstart's mode table gains a node kernel row.

Checks

• npm run build: passes, onBrokenLinks: throw, no broken anchors. All seven anchors the agent links render.
• npm run verify-schema: passes.
• prettier@2.8.8 --check: clean on every changed file.
• UI Capture images: WebP, all under 75 KB.

Merge order

• The UI Capture page documents features that ship in keploy/api-server#2277 and keploy/enterprise-ui#1925. Merge this once both are released.
• keploy/enterprise#2636 links the capture loss page, so this has to be live before that ships.