docs: fix two stale claims in LIMITATIONS.md

[rajnisht7]

Summary

LIMITATIONS.md said "Only a Python reference SDK exists" and "No metrics projector or AGT adapter is implemented." Both are false today a full TypeScript SDK (packages/typescript/), OTelMetricEmitter, and four AGT adapter modules already ship and are tested. Both lines were true when written but never updated after the features landed in later PRs. Replaced with the actual current gap: no adapter yet emits approval.cancelled, approval.execution_, or evidence. lifecycle events, even though those event types are already defined in the schema.

Contract impact

• No wire-contract change
• Backward-compatible contract change with fixtures
• Breaking contract change with migration notes

Evidence

• python tools/sync_schemas.py
• python tools/check_schemas.py
• python conformance/runner/validate.py
• python -m unittest discover -s tests -v
• python -m build

Privacy and security

• No real prompts, source, credentials, personal data, or production identifiers added
• New fields have capture semantics and privacy classification
• Security-sensitive changes received maintainer review

Limits

State what this change does not prove or cover.