docs(skill): make already-AI-first routing silent

[xergioalex]

Summary: when the router detects the repository is already AI-first, it now instructs the agent to route by intent silently instead of emitting a "the repo is already AI-first / routing to the create sub-skill" preamble.

Motivation: that announcement is noise — users invoking a sub-skill (e.g. /dwp-create) on an already-onboarded repo want the flow to begin directly, not a restatement of the detection/routing decision.

What changed: one clarifying clause added to the "already AI-first" line in the router SKILL.md. No behavior change to onboarding, no public-surface change (slash commands, .dwp/ convention, setup.sh flags all unchanged).

Risk: none — prompt-wording refinement only.

Summary

Type

• feat — new behavior
• fix — bug fix
• docs — documentation only
• chore — repo maintenance
• test — adding tests
• ci — CI configuration
• refactor — no user-visible change

Scope

• Modified runtime skill (anything under skills/deepworkplan/)
• Modified dev infrastructure (anything outside skills/deepworkplan/)

Pre-merge checklist

• shellcheck setup.sh skills/deepworkplan/shared/context.sh scripts/*.sh passes
• bats tests/ passes
• python3 scripts/validate-frontmatter.py passes
• No runtime file added outside skills/deepworkplan/ (and no dev-infra file added inside it)
• .dwp/ stays gitignored — no plan output committed
• No name: deepworkplan_* (snake_case) introduced — kebab-case only
• No homepage: field introduced — use documentation_url:
• No bash 4+ idioms (mapfile, declare -A, ${var^^}) introduced
• CHANGELOG.md NOT hand-edited and version: fields NOT hand-bumped (the auto-release bot owns them)
• Public surface preserved (the six /deepworkplan-* slash commands, the .dwp/ convention, setup.sh flags, skill name fields) — or major version bumped (feat(...)!:) with a migration note
• Commit messages follow <type>(<scope>): description format

Test plan

• [ ]
• [ ]

Risks

Breaking changes (only if applicable)