Improve agent-team README onboarding

[pate0304]

What changed

• lead with Codesemble's repository-aware agent-team value and move Quick Start above the technical explanation
• use the installed namespaced $codsemble:* skill commands and an immutable v0.2 candidate ref
• explain how the primary Codex thread controls orchestration, how generated specialists are used, and why installed roles differ from active workers
• add a concrete repository-evidence-to-team example
• state explicitly that the 111-entry catalog is a primitive library, not a fixed installed roster or concurrency target
• update the merged-but-unreleased v0.2 status and make contribution paths more actionable
• regenerate the source checksum manifest for the README change

Why

GitHub visitors should understand within seconds what Codesemble creates, who controls its agents, why its teams are dynamic, and how to try the current candidate safely.

Validation

• three bounded read-only agent reviews for product clarity, factual accuracy, and onboarding discoverability
• final agent re-reviews passed with no residual blockers
• 140/140 tests across 20 files
• TypeScript, build, catalog, repository, and deterministic bundled-CLI validation passed
• 120 source checksums, 128-component SBOM, and deterministic 12-file archive verified
• all README local links and anchors verified
• npm audit reports zero vulnerabilities