fix(release): add proper newline after New Contributors section in cliff template

[jdx]

Summary

• Fixes the changelog formatting issue where there was an extra blank line between the last commit and the New Contributors section
• Removes unnecessary whitespace for cleaner changelog formatting

Problem

The changelog in PR #6192 and release v2025.9.1 had an extra blank line between the bug fixes and the New Contributors section:

### 🐛 Bug Fixes

- python nested venv path order by [@elvismacak]...
- resolve immutable release workflow...


### New Contributors

This extra blank line made the changelog look inconsistent and poorly formatted.

Solution

Changed the cliff.toml template to:

1. Add - to the end of {% endfor -%} on line 41 to strip trailing whitespace
2. Remove the blank line between the if statement and "### New Contributors" heading

The template now properly strips whitespace between sections while maintaining clean separation.

Test

Tested by generating release notes for v2025.9.1:

git cliff --strip all --tag v2025.9.1 v2025.9.0..v2025.9.1

Result shows proper formatting with no extra blank lines:

### 🐛 Bug Fixes

- python nested venv path order by [@elvismacak]...
- resolve immutable release workflow...

### New Contributors

- @elvismacak made their first contribution...

Test plan

• Generate changelog with git cliff and verify no extra blank lines
• Verify proper spacing between all sections
• Check that version headers are properly separated

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

Fixes changelog formatting where the New Contributors section was incorrectly running into the next version header due to a template newline handling issue.

• Changed Jinja template to properly preserve newlines after the contributor list
• Added a blank line between the contributors section and subsequent content

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[github-actions]

Hyperfine Performance

mise x -- echo

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.1 x -- echo	20.2 ± 0.8	18.7	23.4	1.00
mise x -- echo	21.0 ± 1.0	19.3	26.2	1.04 ± 0.06

mise env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.1 env	19.4 ± 0.8	18.1	24.1	1.00
mise env	20.2 ± 0.9	18.4	23.8	1.04 ± 0.06

mise hook-env

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.1 hook-env	19.0 ± 0.7	17.7	21.7	1.00
mise hook-env	19.2 ± 0.9	17.8	24.5	1.01 ± 0.06

mise ls

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
mise-2025.9.1 ls	17.2 ± 0.6	16.0	19.2	1.00 ± 0.05
mise ls	17.1 ± 0.7	16.0	19.5	1.00

xtasks/test/perf

Command	mise-2025.9.1	mise	Variance
install (cached)	166ms	✅ 106ms	+56%
ls (cached)	63ms	63ms	+0%
bin-paths (cached)	67ms	67ms	+0%
task-ls (cached)	474ms	486ms	-2%

✅ Performance improvement: install cached is 56%