add error context to ctf contract calls

[notyrjo]

The three contract read calls in ctf.rs (getConditionId, getCollectionId, getPositionId) propagate errors with ? but without context, so when they fail the user sees a raw RPC or transport error with no indication of which operation failed.

This adds .context() messages consistent with the error handling pattern used elsewhere in the codebase.

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Note

Low Risk
Read-only CLI error messaging only; no behavior, auth, or on-chain logic changes.

Overview
Adds anyhow::Context messages on the three read-only CTF contract calls in ctf.rs (getConditionId, getCollectionId, getPositionId) so RPC/transport failures name the operation instead of surfacing a bare error.

This matches the existing pattern on write paths (e.g. "Split position failed") and on input parsing in the same file.

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