Add supported-chains cmd & Improve Error Messages

[ejacquier]

Supported Chains

• Added cre workflow supported-chains command (sorted alphabetically)

📊 Error Handling Improvements

#	Top Error (CSV)	Count	Improvement
1	no project settings file found	321	Now: clearer message ("no CRE project found") + suggests cre init, --project-root, or cd into project
2	Script not found "cre-compile"	303	Now: explains it comes from @chainlink/cre-sdk + suggests bun install / cre update
3	no RPC URLs found	178	Now: shows which target failed + suggests checking rpcs section and --supported-chains
4	failed to parse private key	159	Now: shows actual vs expected length (64 hex chars) + lists common mistakes
5	workflow.yaml: no such file or directory	155	Now: clearer message ("workflow settings file not found") + suggests cre workflow init or checking path

[github-actions]

👋 ejacquier, thanks for creating this pull request!

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[timothyF95]

Don't we have a generalised rpc check in the root of the cmd package?

[ejacquier]

Not quite. cmd/root.go has isLoadDeploymentRPC() which decides whether to load RPC settings (for deploy/pause/activate/delete). That's a
config-loading gate, not a validation error.

The merge-base changed after approval.

[timothyF95]

We're missing cre workflow list during merge conflict resolution