fix: preserve merged headers in repository-meta fetch options (spread order bug)

[coderabbitai]

Summary

In shared/utils/repository-meta.ts, the object spread order when building fetch options causes ...options to overwrite the entire headers object, discarding the merged User-Agent: npmx header (and any other headers built up prior to the spread).

This is a pre-existing issue that originated in app/composables/useRepoMeta.ts on main and was moved as-is into the new shared utility in #2764.

Problem

The current pattern (at 8 locations) is:

// Incorrect — outer ...options clobbers the headers object
{ headers: { 'User-Agent': 'npmx', ...options.headers }, ...options }

Fix

Spread options first, then override headers with the merged value:

// Correct — User-Agent preserved, caller headers merged in
{ ...options, headers: { 'User-Agent': 'npmx', ...options.headers } }

Affected locations

• shared/utils/repository-meta.ts lines 118, 160, 197, 236, 275, 321, 422, 466

References

• Identified during review of refactor: extract repo metadata utils from composable #2764 (comment: refactor: extract repo metadata utils from composable #2764 (comment))
• Requested by @serhalp