fix: restore Python 3.10/3.11 support and report MCP version

- Drop backslash from f-string expression in markdown/html.py
- That syntax needs 3.12+ (PEP 701) and broke import on 3.10/3.11
- Add Python matrix 3.10/3.12/3.14/3.15 to the Gitea testing workflow
- Pass project_version() to MCPServer; serverInfo.version was empty
- Cover the reported version with an in-memory MCP client test
- Swap deprecated click.get_text_stream for sys.stdin.isatty()
- Add explicit encoding to native host shim and manifest writes
- Add explicit encoding to the registry lock file open
- Add explicit encoding to every read_text/write_text call in tests
- Bump version to 0.16.10 in pyproject.toml and extension/manifest.json
- Move .python-version to 3.15 and refresh uv.lock

Extension code is unchanged; only the manifest version string moved.

Verified with 778 tests on 3.10 through 3.15, plus a strict run using -X warn_default_encoding with EncodingWarning and DeprecationWarning as errors.

tests/test_cli.py

@@ -208,7 +208,7 @@ def test_write_native_host_exe_unix(tmp_path):
     write_native_host_exe(host)
 
   assert host.exists()
-  content = host.read_text()
+  content = host.read_text(encoding="utf-8")
   assert content.startswith(f"#!{sys.executable}")
   assert "from browser_cli.native.host import main" in content
   assert host.stat().st_mode & 0o111  # executable bit set