Fix version to single bump (9029) and update CLAUDE.md versioning rules

CLAUDE.md: Rewrite the "Version and date bump" subsection to document that:
- Exactly ONE version bump is allowed per PR (PRs are squash-merged into one
  commit on the default branch, so one commit = one version increment)
- The correct version is computed from git history:
    currentversion="${currenttag}.$((commits_since_tag + 9001 + 1))"
  with the +1 accounting for the PR's own squash commit not yet on the
  default branch
- Fall back to incrementing DESCRIPTION's version by 1 if git describe fails
- The Date: field tracks the date of the *last* PR commit (updated each time)

DESCRIPTION / NEWS.md: Correct the version from 3.0.1.9030 back to 3.0.1.9029.
Two version bumps were made across two commits in this PR; since it will be
squash-merged as one commit only one bump is correct. Also update Date to
today (2026-03-07).

https://claude.ai/code/session_01Cp154UtssHg84bw38xiiTG

CLAUDE.md

@@ -148,24 +148,34 @@ Version format: `major.minor.patch.dev` (e.g., `3.0.1.9021`)
 
 ### Version and date bump required for every PR
 
-Before opening a pull request, always increment the four-digit dev counter by 1 in **both** of these files:
+All PRs are **squash-merged**, so each PR lands as exactly **one commit** on the default branch. Version numbers are kept in sync with the cumulative commit count since the last released tag. Therefore **exactly one version bump is allowed per PR**, regardless of how many intermediate commits are made on the branch.
 
-1. **`DESCRIPTION`** — the `Version:` field:
-   ```
-   Version: 3.0.1.9021  →  Version: 3.0.1.9022
-   ```
+#### Computing the correct version number
 
-2. **`NEWS.md`** — the top-level heading:
-   ```
-   # AMR 3.0.1.9021  →  # AMR 3.0.1.9022
-   ```
+Run the following from the repo root to determine the version string to use:
 
-Read the current version from `DESCRIPTION`, add 1 to the last numeric component, and write the new version to both files in the same commit as the rest of the PR changes.
+```bash
+currenttag=$(git describe --tags --abbrev=0 | sed 's/v//')
+currenttagfull=$(git describe --tags --abbrev=0)
+defaultbranch=$(git branch | cut -c 3- | grep -E '^master$|^main$')
+currentcommit=$(git rev-list --count ${currenttagfull}..${defaultbranch})
+currentversion="${currenttag}.$((currentcommit + 9001 + 1))"
+echo "$currentversion"
+```
 
-Also bump the date to the current date in **`DESCRIPTION`**, where it's in the `Date:` field in ISO format:
+The `+ 1` accounts for the fact that this PR's squash commit is not yet on the default branch. Set **both** of these files to the resulting version string (and only once per PR, even across multiple commits):
+
+1. **`DESCRIPTION`** — the `Version:` field
+2. **`NEWS.md`** — the top-level heading `# AMR <version>`
+
+If `git describe` fails (e.g. no tags exist in the environment), fall back to reading the current version from `DESCRIPTION` and adding 1 to the last numeric component — but only if no bump has already been made in this PR.
+
+#### Date field
+
+The `Date:` field in `DESCRIPTION` must reflect the date of the **last commit to the PR** (not the first), in ISO format. Update it with every commit so it is always current:
 
 ```
-Date: 2025-12-31
+Date: 2026-03-07
 ```
 
 ## Internal State

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: AMR
-Version: 3.0.1.9030
-Date: 2026-03-06
+Version: 3.0.1.9029
+Date: 2026-03-07
 Title: Antimicrobial Resistance Data Analysis
 Description: Functions to simplify and standardise antimicrobial resistance (AMR)
   data analysis and to work with microbial and antimicrobial properties by

NEWS.md

@@ -1,4 +1,4 @@
-# AMR 3.0.1.9030
+# AMR 3.0.1.9029
 
 ### New
 * Integration with the **tidymodels** framework to allow seamless use of SIR, MIC and disk data in modelling pipelines via `recipes`