docs(agents): de-alkgit the copied process scaffolding

The .opencode agent definitions and docs/sdd_process.md were copied
verbatim from alkgit; replace the stale project references with
alkssh-shaped ones:

- sdd_process.md: title line named @alkdev/alkgit
- coordinator.md: example spawn prompt named the project and carried
  alkgit constraints (pure protocol crate, gix, feature list)
- implementation-specialist.md: conventions 7-9 were alkgit's
  (gitoxide/no-MPL, sha256/acme features, repo-public auth wording);
  now russh-owns-the-wire, fail-closed mapping features, key reuse
- architect.md: deferral examples named alkgit-admin and the alkhttp
  git-feature shape
- poc-specialist.md: standalone-POC path example /workspace/alkgit-poc1

Verification: docs-only change

docs/sdd_process.md

@@ -2,7 +2,7 @@
 
 ## Overview
 
-This document defines the SDD process for the @alkdev/alkgit project. It
+This document defines the SDD process for the @alkdev/alkssh project. It
 leverages:
 
 - **OpenCode CLI** as the agent execution environment