Merge bitcoindevkit/bdk#2317: ci: pin yoke-derive to 0.8.2 for MSRV

4dc5e5a4fc1fe6d14f6b5457a48596197f45de24 ci: pin yoke-derive to 0.8.2 for MSRV (志宇)

Pull request description:

  ### Description

  The MSRV (1.85.0) CI job is failing. `yoke-derive` 0.8.3 (released 2026-09-15) calls `str::from_utf8` as a method on the `str` type. That form isn't available on Rust 1.85.0, and the crate doesn't declare a `rust-version`, so cargo doesn't avoid it:

  ```
  error[E0599]: no function or associated item named `from_utf8` found for type `str` in the current scope
     --> yoke-derive-0.8.3/src/lib.rs:202:32
      |
  202 |         let underscores = str::from_utf8(&underscores).expect("_ is ASCII and thus UTF-8");
      |                                ^^^^^^^^^ function or associated item not found in `str`
  ```

  `yoke-derive` gets pulled in through `url` -> `idna` -> the `icu_*` crates -> `zerovec` -> `yoke`. This PR pins it to 0.8.2 in `ci/pin-msrv.sh`. Version 0.8.2 calls `core::str::from_utf8` instead, and `yoke` 0.8.3 accepts `yoke-derive ^0.8.2`.

  Failing run: https://github.com/bitcoindevkit/bdk/actions/runs/35182209052/job/105076597730

  ### Notes to the reviewers

  I couldn't build with 1.85.0 locally, so the MSRV CI run on this PR is the real test. I did check that `ci/pin-msrv.sh` runs cleanly from a fresh lockfile and ends up with `yoke-derive` 0.8.2. The last green `master` run (2026-09-12) was before 0.8.3 came out.

  ### Checklists

  #### All Submissions:

  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)

  🤖 Generated with [Claude Code](https://claude.com/claude-code)

ACKs for top commit:
  tvpeter:
    tACK  4dc5e5a4fc1fe6d14f6b5457a48596197f45de24
  noahjoeris:
    tACK 4dc5e5a4fc1fe6d14f6b5457a48596197f45de24

Tree-SHA512: 812f4cf719c9ed4fda07fc90d81149e1d05169d11cd1d785667801cb88479dbf4628c94ba5477048415e718a4fb09ce7060c35850bde1fc0673649c5e4f5ff59