unify zsh+bash shell config; fix zsh startup

Support either shell as the login shell via stow selection (merges the
bashed branch in). shell/ holds shared POSIX env + interactive config;
each shell loads its own rc natively.

- zsh: add .zshenv (sets ZDOTDIR+env early), rename rc -> .zshrc, add
  login-only .zprofile (pyenv --path)
- bash: add ~/.bash_profile + ~/.bashrc stubs, .config/bash/{rc,prompt}
- shell: profile is POSIX env-only (no zsh-rc source); path rewritten
  POSIX + idempotent (flat ~/.local/bin, no subdir recursion); new
  interactive sources aliases/functions + pyenv shims
- drop dead shell/.zprofile symlink; move ZDOTDIR out of exports

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,57 @@
+# My personal dotfiles
+
+To be used with GNU stow.
+
+Goal is a clean-as-possible home directory.
+As much as possible in standard `.config/`, `.local/` and so on.
+
+## Shell architecture (multi-shell)
+
+The config supports **both zsh and bash** from one branch. Pick the login shell
+by which package you `stow`; `shell/` is always stowed. (There used to be a
+separate `bashed` branch — retired; do not recreate it.)
+
+Split by *role*:
+
+- **`shell/`** (shared) — POSIX, shell-agnostic.
+  - `exports`, `path` — environment. `path` is idempotent (safe to source twice).
+  - `aliases`, `functions` — interactive bits, POSIX-safe.
+  - `interactive` — sources `aliases`/`functions`/`extra` + pyenv shims. Loaded
+    by each shell's own rc (brace expansion OK; only zsh/bash source it).
+  - `profile` — POSIX **login env only** (no brace expansion, no rc source).
+    `~/.profile` symlinks to it.
+- **`zsh/`** — `~/.zshenv` (sets `ZDOTDIR`+env, runs for *every* zsh),
+  `$ZDOTDIR/.zshrc` (interactive, sources `shell/interactive`),
+  `$ZDOTDIR/.zprofile` (login-only, pyenv `--path`).
+- **`bash/`** — `~/.bash_profile` (login → sources `~/.bashrc` + pyenv `--path`),
+  `~/.bashrc` (sources `~/.profile` for env, then `~/.config/bash/rc`),
+  `~/.config/bash/rc` (interactive, sources `shell/interactive` + bash bits),
+  `prompt`.
+
+Invariants worth keeping:
+- `ZDOTDIR` belongs in `~/.zshenv` only — it must be set before zsh reads any
+  rc file, so `exports` is too late.
+- Env must reach **non-login interactive** shells: zsh gets it via `.zshenv`
+  (always runs); bash gets it because `.bashrc` re-sources `~/.profile`
+  (idempotent). Don't move env loading out of those two spots.
+- Prompts are necessarily per-shell (`%n@%M` vs `\u@\h`); keep them split.
+
+## Known issues / TODO (next session)
+
+Remaining from the 2026-06-26 review (zsh/bash startup items already fixed):
+
+1. **Clean-home goal leaks:**
+   - `psql/rc`: `HISTFILE ~/.psql_history-:DBNAME` writes a dotfile to `$HOME`.
+     Redirect under `~/.cache`.
+   - `git/config`: `excludesfile = ~/.gitignore`, `attributesfile = ~/.gitattributes`.
+     Move to `~/.config/git/{ignore,attributes}` (git reads `ignore` there by default).
+
+2. **History dirs not created.** `HISTFILE` points at `$XDG_CACHE_HOME/shell/history`,
+   but zsh/bash won't `mkdir` the parent, so history is silently dropped. Need a
+   bootstrap/`mkdir -p`. (The python startup script already does its own mkdir.)
+
+3. **Dead config.** alias `f="$FILE"` — `$FILE` is never set (empty alias);
+   `functions` file is empty; `git/config` carries macOS-only settings
+   (`trustctime`, `precomposeunicode`, mac comments) — dead weight on Arch.
+   `bash/.config/bash/rc` also keeps Homebrew/macOS completion blocks (guarded,
+   harmless, but droppable).