chore(main): release 0.124.0

[release-please]

🤖 I have created a release beep boop

0.124.0 (2025-10-16)

Features

• client: Enable routing cookie and attempt headers for enhanced retries (#12964) (96cfd47), refs #12658
• internal/librariangen: Add nested protos config to repo-config.yaml (#13158) (2c37c8b)
• internal/librariangen: Make repo-config.yaml optional (#13038) (800b556)
• internal/librariangen: Support for "whole repo" libraries (#12976) (4ff4e77)
• stategen: Populate release_exclude_paths for snippets (#12942) (b25be45)

Bug Fixes

• internal/librariangen: Handle multi-versioned modules and root module (#13013) (b0fad5f)
• internal/librariangen: Use TagFormat as the CLI does (#13012) (d24b0f8)
• internal/stategen: Be more conservative about removing OwlBot lines (#13106) (7663fdc)
• internal/stategen: Match input directories more carefully in OwlBot (#13057) (f9efee1)
• internal/stategen: Write state.yaml with the same code as librarian CLI (#12955) (0464d0b)

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[shollyman]

Not releasing week of 2025-09-29 because there's only internal changes, nothing public to expose.

[bhshkh]

Skipping 2025-10-14 because there's only internal changes, nothing public to expose.

[shollyman]

Marking this DO NOT MERGE again as this release is pretty much moribund.

It was created due to a bad reference in a PR for bigtable, and got picked up by the main release. The librariangen and stategen PRs do not affect the release itself, they're part of the librarian build/release infrastructure.

[jskeet]

Closing - this was last updated just before we merged the root module migration PR (not after it, as I'd previously thought) so I don't think there's anything odd to explain.