fix(cli): implement --force flag to protect existing skill files

[alfredo-petri]

Problem

--force is registered in index.ts and described in the README, but has no effect. template.ts calls writeFile() unconditionally without checking whether the file already exists.

This means:

• Users running uipro init a second time silently overwrite their customized skill files
• The --force flag advertised in the README is misleading — it does nothing

Fix

Add a file existence check in generatePlatformFiles before calling writeFile:

• If file exists and --force was not passed → skip with a clear message
• If file exists and --force was passed → overwrite (previous behavior for all cases)
• Propagate force through generateAllPlatformFiles → templateInstall → initCommand

Behavior after this PR

uipro init --ai claude          # skips if SKILL.md already exists, prints warning
uipro init --ai claude --force  # overwrites regardless

🤖 Generated with Claude Code

[mrgoonie]

Summary: This is a focused fix for the advertised --force behavior in the template installer path. It correctly threads the force option through init -> templateInstall -> generatePlatformFiles and prevents accidental overwrite of an existing generated skill file when --force is absent.

Risk level: Low

Mandatory gates:

• Duplicate/prior implementation: clear — searched existing issues/PRs for the force/overwrite behavior and found no overlapping implementation besides this PR.
• Project standards: passed — the change stays inside the CLI init/template generation path and reuses the existing fs access helper pattern.
• Strategic necessity: clear value — avoiding silent overwrites protects user-customized skill files and makes the documented --force flag meaningful.
• CI/checks: missing/unstable — no status checks are reported for this PR in GitHub, and this cron environment does not have bun installed to run the package build.

Findings:

• Critical: none.
• Important: none.
• Suggestion: consider adding a small CLI/template unit or smoke test later for the no-force skip path and the --force overwrite path, because this behavior is easy to regress.

Verdict: APPROVE