Changes

fix(flow): normalize feature branch version suffix (#4144)

## What
Fix `scripts/flow/build/versioning-strategy.ts` feature-branch
version/tag generation so that branch names containing `_` are
normalized as expected.

## Why
The existing TDD test case expects `feature/xxx_yyy` to produce
`v<MAJOR>.<MINOR>.<PATCH>-feature.xxx-yyy`, but the implementation left
`_` untouched.

## How
- In feature-branch handling, normalize `_` -> `-`.
- Keep existing normalization of `/` -> `.`.
- Do **not** convert `-` to `.` (tests expect dashes to remain).

## Test
- `deno test scripts/flow/build/versioning-strategy.test.ts`
 (commit: 1c421d7)