docs(rebrand): rename & rebrand CI → CIAgent across all documentation, templates, and scripts

- README.md: title, project name, CLI commands, .ci/ → .ciagent/, ci-files → ciagent-files, CI Modification → CIAgent Modification
- AGENTS.md: title, project name, architecture tree, agent count (18→19), test count (25→31 suites, 218→370 tests), version (0.4.0→0.6.0), ci-files → ciagent-files, CIConfig → CIAgentConfig, CiMetadata → CIAgentMetadata, .ci/ → .ciagent/
- templates/DECISIONS.md: .ci/audit/ → .ciagent/audit/, ci audit → ciagent audit
- scripts/postinstall.js: CI postinstall → CIAgent postinstall
- scripts/install.sh: CI → CIAgent, ci-init → ciagent-init, INSTALL COMPLETE banner
- opencode/ci/workflows/*.md (11 files): .ci/ → .ciagent/, CI → CIAgent project name, ci-command → ciagent-command usage lines
- opencode/ci/references/*.md (5 files): .ci/ → .ciagent/, CI → CIAgent project name, ci-files → ciagent-files references
- opencode/ci/contexts/*.md (3 files): .ci/ → .ciagent/, CI → CIAgent project name
- opencode/agents/ci-*.md (18 files): .ci/ → .ciagent/, CI → CIAgent project name
- opencode/command/ci-*.md (11 files): CI → CIAgent project name

Preserved: ---ci---/---/ci--- markers, opencode/ci/ dir paths, ci-*.md filenames, ci listProjects()/ci setActiveProject() API names, repo URLs

---ci---
phase: 1
milestone: v0.6
plan: 01-01
task: 01-01-01
status: execute
---/ci---

opencode/command/ci-status.md

@@ -1,5 +1,5 @@
 ---
-description: Show CI project status — current phase, milestone, pipeline stage, decisions, escalations, and requirements coverage
+description: Show CIAgent project status — current phase, milestone, pipeline stage, decisions, escalations, and requirements coverage
 tools:
   read: true
   bash: true
@@ -16,6 +16,6 @@ Arguments: $ARGUMENTS
 </context>
 
 <process>
-Execute the CI status workflow end-to-end.
+Execute the CIAgent status workflow end-to-end.
 Preserve all workflow gates, validations, checkpoints, and routing.
 </process>