Fix waitForConnections vacuous-truth + add loop() test coverage

[AndreLFSMartins]

fix(sdk): waitForConnections treats empty/failed connections as connected

In packages/core, createSession's manageConnections.waitForConnections gate breaks as soon as connections().every(c => c.connected) is true. But connections() returns [] on a failed or empty backend response, and [].every(...) is vacuously true — so the gate resolves on the first poll with zero servers connected, the opposite of what waitForConnections promises. Guarded with conns.length > 0.

The Python SDK already guards this (_async_session.py: if conns and all(...)), so this also restores TS/Python parity.

test(sdk): loop() had no tests

loop() (the "Complete Loop" orchestration) had zero coverage. Adds tests for: happy path, dynamic params(prevResults), when() skips, abortOnError true/false, thrown-error retry, linear vs exponential backoff, and the zero-step / all-skipped edge cases.

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No wire-contract change. npm test + tsc --noEmit green for packages/core.

[rapguit]

Thanks again, Andre — quality PR, easy to review.

Verified locally:

• Bug is real: [].every(...) is vacuously true, and connections() returning [] on a failed/empty response would resolve the gate with zero servers connected. One-line guard (conns.length > 0 &&) is the right fix.
• Python parity: confirmed against packages/python/src/codespar/_async_session.py:1193 — if conns and all(c.connected for c in conns). Same shape, now mirrored in TS.
• Tests: full @codespar/sdk suite passes (95/95) with the change merged onto current main. tsc --noEmit clean.
• loop() coverage: the previously-untested orchestration entrypoint now has 13 tests covering happy path, dynamic params, when() gating, abortOnError, retry policies (linear + exponential), and the vacuous-truth edge cases at the boundaries. Characterization-style tests for those edge cases (success:true on zero/all-skipped steps) are a sensible call — locks current behavior without quietly changing it.

One tiny note for future PRs: a couple of test comments reference docs/fix-core.md (R4 / C2) which doesn't ship in the repo. Harmless — the comments stand on their own — just a heads-up so future readers don't go chasing a missing doc.

Merging.