[deploy-plugin DPB-28] Docs: target-matrix reference + per-target how-tos replace the alpha-minimal page

[rickylabs]

Part of #892 (RFC #891; corpus .llm/runs/plan-deploy-plugin--seed/ r5).

The docs IA from the doc-story forecast: getting-started (plan → up on deno-deploy; the CI split taught where emission is real), the capabilities/doctor reference (unverified vs unsupported vs adapter-not-installed vs credential-unavailable), the migration page (legacy verbs, the one config behavior change), per-target how-tos landing with their adapters. Anti-scope: no capability claims beyond shipped manifests; public-docs hygiene.

Acceptance

• gate: docs accuracy eval green (docs gate)
• gate: every claim traces to a shipped manifest or command

Metadata

Dependencies: DPB-16 (rolling; first tranche with W3)
Delivery shape: docs consolidation