docs: add liaison tracker

[kmishra1204]

Summary

Closes #11.

Adds LIAISON_TRACKER.md as a lightweight liaison roster and cross-WG intake tracker, then links it from the README.

The tracker includes:

• external groups and standards bodies named in the charter, including OpenTelemetry GenAI SIG, OWASP AOS, W3C Trace Context, Agent Trace, Monocle, AGNTCY, and protocol maintainers beyond MCP
• internal AAIF coordination rows for TC, MCP, Goose, Taxonomy/Landscape, Identity and Trust, Security and Privacy, Governance/Risk/Regulatory, Workflows, and Accuracy/Reliability
• explicit TBD owner/cadence fields where no public liaison assignment is visible
• inbound ask and outbound follow-up columns
• an initial intake queue from the public 2026-06-11 and 2026-06-25 meeting minutes
• review checklist to keep private contact details out and owner fields explicit

Validation

• git diff --check
• ASCII check on LIAISON_TRACKER.md
• Checked issue Establish liaison roster and cross-WG intake tracker #11 acceptance criteria against the added tracker and README link

Notes

This intentionally does not assign private liaison roles. It marks unknown owners as TBD so chairs or nominated leads can fill them in publicly later.

[kmishra1204]

Validated this current head after fetching upstream main.

Local checks:

• Branch is one commit ahead and zero behind upstream main
• git diff --check origin/main...fork/codex/liaison-tracker-issue-11
• Changed-file scope is markdown-only: LIAISON_TRACKER.md, README.md
• Relative links in changed markdown resolve inside the branch
• No TODO/FIXME/example placeholder text found in changed files; TBD is intentionally used as an explicit tracker state in this document