Make help text honestly AWS-only; add a cloud parity matrix

[stxkxs]

What

cloudgov is AWS-native today; its provider seams are multi-cloud-shaped but no GCP/Azure provider is implemented. A few command help strings overstated that, and the README had no statement of which clouds each command covers.

Help text

Rewrote command help that used generic cloud/across providers to name AWS:

• inventory — "List all cloud resources across providers" → "List all AWS resources" (Short + Long).
• quota — "…across cloud providers" → "Check AWS service quota utilization vs limits".
• secrets / secrets scan — dropped the false GCP "Cloud Functions" and Azure "App Service settings" scan targets; the scanner only reads AWS surfaces (Lambda env, ECS task defs, EC2 user data, SSM params, CloudFormation outputs), now listed accurately. (It still detects leaked GCP/Azure credentials embedded in those AWS surfaces — a finding type, not a scan target.)
• cost / orphans / drift — "cloud" → "AWS" for consistency.

Parity matrix

README gains a ## Cloud support section: a short statement that the tool is AWS-native with a pluggable provider seam (capability interfaces + registry) making GCP/Azure additive, plus a command × cloud matrix (✅ implemented · ⬡ seam-ready · — n/a) — AWS full across all domains, GCP/Azure seam-ready, k8s for RBAC; offline commands + mcp noted as cloud-agnostic. The pluggable-seam framing (the intentional design) is kept; only present-tense multi-cloud claims were removed.

How it was found / verified

• Audit workflow (4 parallel read-only sweeps): confirmed the README headline was already honest, surfaced the subtle help-string overclaims, and enumerated the 22-command matrix material from the code.
• Adversarial review workflow (honesty-completeness + matrix-accuracy dimensions → verify stage): confirmed no overclaim survived and every matrix row is accurate; its 4 LOW nits are fixed here (inventory/drift H3 headings, cost/orphans/drift Shorts, the Platform footnote — corrected from "RBAC" to IRSA + tenant cluster objects — and mcp added to the matrix note).

Docs-only + help strings; task build / go test ./... / go vet green. Completes backlog T8.