docs: add Traceroute monitor documentation

[danielpaulus]

Summary

Adds Traceroute monitor documentation — three new pages plus navigation:

• detect/uptime-monitoring/traceroute-monitors/overview.mdx — what Traceroute monitors do and how they work, probe protocol reference (TCP / UDP / ICMP / SCTP with protocol-dependent default ports and how destination reach is detected per protocol), results breakdown, and troubleshooting accordions (incl. CAP_NET_RAW for self-hosted agents)
• detect/uptime-monitoring/traceroute-monitors/configuration.mdx — all request fields with defaults/ranges, assertions (Latency / Hop Count / Packet Loss), response-time limits, the JSON response schema, frequency (30s floor, SIM-283), scheduling & locations
• constructs/traceroute-monitor.mdx — CLI construct reference: TracerouteMonitor, TracerouteRequest, and TracerouteAssertionBuilder with basic + advanced examples and full parameter tables
• docs.json — nav entries for the Traceroute Monitors group (after ICMP Monitors) and constructs/traceroute-monitor; canonical URLs added and sitemap.xml regenerated

All content is verified against main of the monorepo (go-runner executor, webapp builder & model defaults, public-API schema) and of checkly-cli (construct sources) — including the protocol-dependent port defaults from SIM-311 (443 TCP / 33434 UDP+SCTP) and the responseTime('avg'|'min'|'max'|'stdDev') assertion-builder signature.

Test plan

• Mintlify renders all three pages; sidebar nav and cross-page links/anchors resolve

Before GA

• Add screenshots: overview (light/dark), request configuration panel, results detail page

[mintlify]

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Project	Status	Preview	Updated (UTC)
checkly-422f444a	🟢 Ready	View Preview	Jul 8, 2026, 1:42 PM

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[danielpaulus]

Accuracy fixes after checking the pages against main of the monorepo and checkly-cli (landed in c8b0088, alongside the main-merge/sitemap work):

• TracerouteAssertionBuilder.responseTime() takes the RTT property as an argument — responseTime('max').lessThan(200). The previously documented chained form (responseTime().avg().lessThan(50)) doesn't exist and wouldn't compile (packages/cli/src/constructs/traceroute-assertion.ts).
• Port defaults are protocol-dependent everywhere since SIM-311: 443 for TCP, 33434 for UDP/SCTP in web UI, CLI, and API. Removed the stale note claiming CLI/API default to 443 for all non-ICMP protocols.
• JSON schema: ICMP responses report the unused fallback port: 443, not 0 (the backend strips the port on input, the runner fills the default). omitempty fields (main_host, rtt, asn, aws_*, finalHopLatency) are absent from the JSON when unset, not empty.
• SCTP destination detection happens via ICMP Destination Unreachable only — the runner never captures direct SCTP ABORT/INIT-ACK replies (the raw send socket is closed right after the probe; there's no SCTP listener).
• Minor: TTL-expiry wording (the responding router drops the probe, it doesn't forward it), open-port advice scoped to TCP (UDP/SCTP need a closed port), and a note that CAP_NET_RAW is required for all Traceroute protocols — SCTP is just the case that surfaces an explicit socket error.