Tests, licence, and the tooling to keep the repo consistent

A test suite with no dependencies beyond bash and the Python standard
library, run by one command:

  scripts/test.sh                    (or: make test)
  scripts/test.sh --windows [host]   adds the PowerShell suite over SSH

- tests/static.sh: script syntax, JSON validity, VERSION against the widget
  manifest and CHANGELOG, providers.json against the kinds, probes and checks
  the code implements (and ids that would shadow a command), qmllint and
  shellcheck when installed.
- tests/python: unit tests for cm-json.py - providers and the column contract
  bash depends on, the original three scaffolds byte for byte, every
  catalogue parser and the cache, session scan/dismiss/repair, rename,
  defaults, health, the cost guard.
- tests/cli: the CLI in a sandbox with its own HOME, CM_ROOT,
  CLAUDE_CONFIG_DIR and a file-only vault, against fake Ollama, LM Studio,
  keyed-gateway and proxy servers - preflight, presets, models, doctor, a real
  switch, sessions, and the key helper under a rename race.
- tests/windows: the same idea on a Windows host, with USERPROFILE pointed at
  a temp folder so the real install is never touched.

Also: MIT licence, CHANGELOG.md reconstructed from history, .editorconfig and
.gitattributes pinning LF everywhere (what the tree already is), and
scripts/bump-version.sh, since the version lives in two files and drifted
once before.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,8 @@
+# LF in every working tree, Windows checkouts included. A CRLF shell script
+# fails its #! line, and the packages are built from a Windows checkout
+# (scripts/build-package.ps1 normalises too, as a backstop).
+* text=auto eol=lf
+
+*.png binary
+*.jpg binary
+*.ico binary