docs: migrate affinity users to the first-class provider

[rjcloudsigma]

Summary

• mark openclaw-taas-affinity as a legacy compatibility plugin
• direct all new CloudSigma users to @cloudsigma/openclaw-taas-provider
• document supported/unsupported topology combinations
• add controlled migration, verification, rollback, and staged-version guidance
• warn loudly at startup when the literal cloudsigma provider owner is also enabled
• add the missing manifest display name so ClawHub validation is clean

Why

OpenClaw selects a literal provider owner before an alias hook. Running this optimizer beside the first-class CloudSigma provider does not compose: the provider handles inference while this plugin's outbound affinity hooks do not execute. The result can look healthy while silently losing session affinity.

Legacy static-provider + optimizer-only hosts (including Rufus) remain temporarily supported until the first-class provider release passes Snowcrash canaries.

Verification

• npm test — typecheck, smoke, 43 Node tests
• npm run build
• npx -y clawhub@0.21.0 package validate . --json — pass, 0 warnings/issues
• git diff --check

Release order

Do not release this migration notice before the parity-capable provider is merged, released, and canaried. This PR does not deprecate/archive the package or change dependencies.

Related provider PR: cloudsigma/openclaw-taas-provider#2
Canonical PRD: https://csigma.atlassian.net/wiki/spaces/DEVOPS/pages/2126708758