v0.1.0.0 feat: multi-store support (EGB-281) (#1)

* feat: multi-store support via .secrets-store + --store flag

Layer four-rule store resolution on top of the existing SECRETS_DIR primitive
so users can manage multiple isolated encrypted stores (work vs personal,
per-client, etc.) without giving up the tool's small-bash-script pitch.

Resolution order (highest first):
  1. --store <dir>  flag (parsed in main pre-pass)
  2. .secrets-store file in cwd or any ancestor up to $HOME
  3. SECRETS_DIR    env var (legacy escape hatch)
  4. ~/.secrets     default

resolve_store() updates both SECRETS_DIR and KEY_FILE so existing single-store
codepaths just work. New cmd_which / where / status report the active store.
cmd_init, push, pull, push_workspaces, pull_workspaces, list, rm, rekey, run,
which all call resolve_store at entry.

Hardening from the EGB-281 adversarial review:
- F1: cmd_run EXIT trap is now a named function (not string-interpolated),
  so paths with apostrophes still get plaintext cleaned up
- F2: symlinked .secrets-store files are skipped, never read
- F3/F4: --store flag rejects flag-shaped values and empty --store=
- F5: HOME unset is detected up-front with a directed error
- F11: check_initialized / check_key give context-aware errors that name
  both recovery paths (git clone vs secrets init) when a teammate clones
  a project bound to a non-existent store on their machine

Tests: 37 → 66 (29 new). HOME=\$TEST_TMPDIR added to test setup so the
walk-up logic stays bounded inside fixtures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* docs: add Multiple stores section to README

Five subsections walk users through: how store resolution works, how to
set up a second store on a machine, how to bind a project, how teammates
join a bound project, and how to undo or change a binding. SECRETS_DIR
table entry now points readers at the new --store flag and .secrets-store
file as the preferred mechanisms.

* chore: bump version and changelog (v0.1.0.0)

First formal release. EGB-281 adds multi-store support; this commit
seeds the VERSION file (4-digit MAJOR.MINOR.PATCH.MICRO) and the
CHANGELOG.md.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,39 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to a four-digit MAJOR.MINOR.PATCH.MICRO version scheme.
+
+## [0.1.0.0] - 2026-05-09
+
+### Added
+
+- **Multiple stores per user.** Run `secrets push` and `secrets pull` against any encrypted store directory you choose, not just `~/.secrets/`. Use cases: keep work secrets isolated from personal, run a separate store per client, or onboard a teammate to one project without giving them every other project's keys.
+- **`.secrets-store` file** for per-project bindings. Drop a one-line file at the project root (e.g. `echo work > .secrets-store && git add .secrets-store && git commit`) and every machine that clones the project automatically uses `~/.secrets-work/` for that repo. No env var to remember, no per-machine setup.
+- **`--store <dir>` flag** for one-shot overrides on any subcommand. `secrets --store ~/.secrets-clientA pull myapp` works without touching files. Bare names like `--store work` expand to `$HOME/.secrets-work`. `--store default` is sugar for `~/.secrets`.
+- **`secrets which`** prints the active store path and which rule chose it (flag, `.secrets-store` file, env var, or default). Aliases: `secrets where`, `secrets status`.
+- **Directed errors for teammate onboarding.** When `.secrets-store` resolves to an uninitialized store or one missing `key.txt`, the error message names both recovery paths: `git clone <remote>` to join an existing store, or `secrets --store <name> init` to start fresh.
+- **Active-store echo.** `secrets push` and `secrets pull` print `==> Store: <path> (from <source>)` whenever a non-default store is active, so wrong-store mistakes surface immediately.
+
+### Changed
+
+- `secrets list` now hints at `secrets which` when a non-default store is active.
+- `cmd_help` documents the four-rule resolution order (`--store` > `.secrets-store` file > `SECRETS_DIR` > default).
+- Error messages for missing init / missing key file are now context-aware: they distinguish between "default store on a fresh machine" and "non-default store referenced by `.secrets-store`."
+
+### Security
+
+- **Path expansion in `.secrets-store` is literal-only.** No `eval`, no `$VAR` interpolation, no `$(...)` execution. A committed `.secrets-store` containing `$(rm -rf ~)` reads as plain text, not as a command.
+- **Walk-up bounded by `$HOME`.** `secrets` never reads `$HOME/.secrets-store`, never walks past `$HOME` to `/`, and never follows symlinked `.secrets-store` files. Symlinks (potential supply-chain attack via committed link to `~/.aws/credentials` or similar) are ignored.
+- **`KEY_FILE` re-derives after `--store` switches stores.** Previously, calling `secrets pull --store other` would have decrypted ciphertext from the new store using the default store's key. Now `secrets` updates both `SECRETS_DIR` and `KEY_FILE` together inside `resolve_store()`.
+- **`secrets run` cleanup survives paths with apostrophes.** The EXIT trap is now a named function rather than a string-interpolated command, so projects at e.g. `/Users/you/Mom's Mac/code` still get plaintext cleared after the wrapped command exits.
+- **Test isolation:** the bats suite now sets `HOME=$TEST_TMPDIR` so `.secrets-store` walk-up cannot wander into the developer's real home directory.
+- **`--store` flag value validation.** Empty values (`--store=`) and flag-shaped values (`--store --workspaces`) are rejected with directed errors instead of silently mapping to `~/.secrets-`-something.
+- **Unset `HOME` is detected** with a directed error before the script tries to expand it. Helps cron, sudo without `-H`, and minimal CI runners.
+
+### Tests
+
+- 37 → 66 tests. New coverage: store resolution rules and precedence, walk-up boundaries, command-injection prevention, key-file re-derivation across stores, teammate-onboarding error path, monorepo workspace binding, F1–F5 adversarial regressions.
+
+[0.1.0.0]: https://github.com/bmajewski/secrets/releases/tag/v0.1.0.0