FastStrata v0.2.0

The fixes from two independent code audits of v0.1.1 (the server's routes for the gateway, the check of Python's
installer, the tests the CI runs), and the context's cache named apart from the model's Q4 / Q3. The engine is the
same as in v0.1.0 and v0.1.1: this release carries the same ready-made
strata-poly-windows-x64-3ba1bf3a4bf413eb.zip.

• The context's memory (the attention cache) is named apart from the model's Q4 / Q3: setup's menu says "up to 144K
  context with an 8-bit cache", the context question says what the cache is, and the README explains the two.
• The server's /completion and /tokenize (what the gateway sends) refuse a web page of another site without an
  API key, as /v1/* does: before, any site open in the browser could have the model write on the PC's card.
• An engine error in the middle of a streamed /completion reaches the gateway as an error event and [DONE], no
  longer as a second HTTP response written into the stream; the API monitor shows /completion's answer and speed.
• The web app's pages cannot be shown in another site's frame (X-Frame-Options, frame-ancestors).
• Where setup downloads python.org's Python 3.12 installer (no Python and no winget), it runs it only with the
  pinned SHA-256; START-HERE.bat checks the same.
• The CI runs the server's tests too (every serve/test_*.py against the mock engine), and Dependabot looks at the
  pinned packages once a month.