feat: add workflow policy packs

[alchemistklk]

Summary

• Adds prompt-time Workflow Policy Pack support with explicit role bindings via roles.<role>.policyPack.
• Adds internal/workflowpolicy to load, validate, and resolve built-in/file packs, including bundled matt-series JSON.
• Injects resolved policy text into planner, reviewer, fixer, and worker prompts before custom instructions and before Looper lifecycle/output contracts.
• Exposes active bindings through config/status/prompt preview and preserves CONTEXT.md as the project glossary for the new domain terms.

Validation

• gofmt -l .
• VISUAL= go test ./...
• go vet ./...
• go build ./...

Note: an initial go test ./... run hit an existing flaky internal/agent timeout; the focused test passed immediately, and the full suite passed on retry with VISUAL=.