docs: weekly Copilot Agents Guide update (2026-07-31)

[soyalejolopez]

Corrects lifecycle, licensing, and FastTrack-scope claims in the Copilot Agents Guide against current first-party Microsoft documentation.

• Researcher: Critique and Model Council documented as Frontier-gated research modes; removed the incorrect "Critique (default)" claim and the duplicated 25-query quota from the capabilities list.
• Workflows agent: replaced the unsourced "Preview / rolling out in Frontier" lifecycle claim with the documented "Available"; English only.
• Copilot Cowork: corrected from Frontier-gated to generally available in tier-1 languages; enumerated all prerequisites and removed "Immediate" availability framing, since usage-based billing and subprocessor approval are required first.
• SharePoint agents: removed undocumented metadata-enrichment and Lists claims; documented the 20-source-item cap and Teams group/meeting/channel sharing (1:1 chat not supported).
• Copilot Studio: split external A2A (classic, GA) from connected agents (new experience, preview); noted that agents cannot be transferred between the classic and new experiences; computer use is GA and covers browser and Windows desktop UI automation; replaced the model list with a pointer to current documentation; "message credits" -> Copilot Credits.
• Declarative agent licensing rewritten to reflect that access and billing depend on the agent's grounding and capabilities.
• Agents Toolkit: separated Microsoft 365 Agents Toolkit, Microsoft 365 Agents SDK, and Teams SDK; removed the claim that A2A is provided by the Toolkit.
• FastTrack scope: "deployment support" -> "remote guidance" in badges, matrix row, and README; added the published channel limitation for custom engine agents (Teams, Microsoft 365 Copilot, SharePoint); removed the change-management claim, which is outside the published benefit.
• Removed the "Composability Advantage" block and the paired scenario card, which asserted an undocumented Cowork/Copilot Studio invocation bridge.
• Fixed the broken footer anchor to #microsoft-365-copilot-agents.

Validation: JSX parse of the embedded Babel block (with a negative control), strict UTF-8 decode, catalog metadata check and stats check, and a rendered smoke test across all agent/tab views with no console errors.

All claims are sourced from public first-party Microsoft documentation.