fix(lm15): support targets (e.g. wasm) without ssl, fcntl, or home directory

[adriaanm]

Push usage of these unsupported features out of module scope, and into the code paths that need them, so that import lm15 succeeds on CPython for wasm32-wasip2.

Each failure was a platform assumption made at module scope, where nothing can recover from it:

• _authlock picked its locking primitive with if os.name == "posix": import fcntl. WASI reports posix but does not ship fcntl.

• auth resolved three credential-path constants with Path("~/...").expanduser(), which raises RuntimeError wherever no home directory can be determined.

• Both transports imported ssl at module scope, and componentize-py's embedded libpython has no _ssl. TLS moves into _ssl.py, which imports ssl plainly because it cannot work without it, and which nothing imports until a request names an https URL. That placement is also what keeps its except ssl.SSLError clauses ordinary, an except clause being evaluated whenever an exception passes it — plain-HTTP errors included.

[MaximeRivest]

Merged, thanks — exactly the right shape (feature-detect the primitive, and pull ssl in only when https is asked for).

Two follow-ups landed on top in b171d75:

• The no-locking refusal is now NotConfiguredError, which is what lm15-ts raises for the same host limitation; UnsupportedFeatureError is the provider-adapter bucket. Same hint either way: set LM15_LOCK_DIR or pass an explicit credential.
• _lock_dir() still resolved ~/.cache with expanduser(), so on a host with no home the bare RuntimeError fired before your branch could. Same error class from there now.

Plus tests that run each reduced target in a fresh interpreter (no ssl, no home, no fcntl/msvcrt) and a changelog entry.