feat(cli): emit rules in Kilo flat builds

Start with issue #744 and its Kilo profile, configuration resolution, and runtime contract, then trace aidd framework build --target kilo --flat. Verify the implementation against the acceptance criteria: generated namespaced rules are placed at the profile-resolved location, configuration preserves user instructions, repeated builds are idempotent, and a clean-project archive is discoverable by a supported Kilo runtime.

Problem

Kilo flat support from #744 will make it possible to distribute framework artifacts for Kilo. Canonical plugin rules would still be absent from that output.

This is separate from #788, which guides direct generation inside a host project. This issue distributes canonical plugin rules through aidd framework build --target kilo --flat.

Scope

• Materialize canonical plugin rules/ into namespaced Markdown files under the Kilo rules location resolved by the Kilo profile.
• Merge generated rule references into the resolved Kilo project configuration without deleting or reordering user-owned instructions entries.
• Make repeated builds idempotent and preserve relative paths, rule scope, and existing user configuration.
• Cover empty configuration, existing instructions, repeated builds, and a flat archive installed into a clean project.

Acceptance criteria

• A plugin rule is present in a Kilo flat build at the location returned by the Kilo profile.
• The Kilo configuration references generated rules while preserving every existing user-owned instructions entry.
• Rebuilding neither duplicates generated entries nor alters user-owned entries.
• The generated rule is discoverable by a supported Kilo runtime.

Dependency

Blocked by #744. That issue owns the Kilo profile, including its configuration resolution and runtime contract; this issue must use that contract rather than duplicate it.

Out of scope

• Direct artifact generation in a project, owned by #788.
• Kilo lifecycle hooks and plugins, owned by #744.
• OpenCode flat output, owned by #789.
• Markdown commands under .kilo/commands/: Kilo does not document that as a native artifact surface. A future command capability, if needed, requires its own plugin-backed product decision.