zsh: fix dead source URL (5.9 moved to /pub/old/)

[bryan-minimal]

https://www.zsh.org/pub/zsh-5.9.tar.xz now returns 404 — zsh.org moved older releases under /pub/old/, so zsh fails to build (source can't be fetched).

Fix: point at https://www.zsh.org/pub/old/zsh-%{version}.tar.xz, which serves the identical tarball — sha256 9b8d1ecedd... unchanged (verified by download). Content-identical URL swap; no version/behavior change.

Found by the reproducibility audit (landed as build_failed with the 404 in its log).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Updated the download source for the zsh package.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: d7c7561a-5df6-4bee-9c09-dac577d4d1b5

📥 Commits

Reviewing files that changed from the base of the PR and between 263ba22 and fca7bc9.

📒 Files selected for processing (1)

• packages/zsh/build.ncl

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📝 Walkthrough

Walkthrough

The download URL for the zsh source tarball in packages/zsh/build.ncl is updated from https://www.zsh.org/pub/zsh-%{version}.tar.xz to https://www.zsh.org/pub/old/zsh-%{version}.tar.xz. No other fields are modified.

Changes

zsh source URL fix

Layer / File(s)	Summary
Update zsh tarball download URL packages/zsh/build.ncl	The url field in the Source definition is changed to use the /pub/old/ path on zsh.org, pointing to the archived release location.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

A bunny hopped by, noticed the link had gone stale,
The old pub path was missing, the download would fail.
One line was swapped, the /old/ now in place,
The tarball fetched cleanly, a hop and a grace.
🐇✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: fixing a dead source URL for zsh 5.9 by updating it to the /pub/old/ path.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bryan/zsh-source-url

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