4 remaining ignored tests require orchard crate test-dependencies

[arya2]

Context

Following the Transaction newtype migration (#10461), 21 of the original 25 ignored tests have been restored. The remaining 4 all require constructing or modifying orchard::Bundle objects from scratch, which needs the orchard crate's testing module (gated behind feature = "test-dependencies").

Blocker

Enabling zcash_primitives/test-dependencies from Zebra fails due to a proptest version conflict:

• zcash_primitives requires proptest >= 1.0, < 1.7
• Zebra uses proptest 1.10.0

Until librustzcash updates its proptest version bound (or Zebra downgrades), we cannot access orchard::bundle::testing::arb_bundle or the test-gated constructors.

Remaining Ignored Tests

Test	What it needs	File
v5_with_duplicate_orchard_action	Duplicate an orchard action within a bundle (requires modifying the action list and proof)	zebra-consensus/src/transaction/tests.rs
coinbase_outputs_are_decryptable_for_fake_v5_blocks	Construct orchard actions with specific note encryption fields from test vectors	zebra-consensus/src/transaction/tests.rs
shielded_outputs_are_not_decryptable_for_fake_v5_blocks	Same as above	zebra-consensus/src/transaction/tests.rs
mempool_skip_accepts_block_with_garbage_orchard_proofs	Construct an orchard bundle with intentionally invalid (garbage) proofs	zebra-consensus/src/transaction/tests.rs

Why byte-level manipulation doesn't work

Unlike sapling (where spends/outputs/proofs are in separate contiguous sections that can be spliced), the orchard bundle format interleaves actions with their commitments in a way that makes:

• Action duplication require updating the action count, proof size, and binding signature
• Custom action construction require valid curve points for commitments (cv, cmx, nullifier, rk) that satisfy algebraic relationships
• Garbage proof insertion require a validly-structured proof blob of the correct size within a properly-formed bundle

Resolution paths

1. Update proptest bound in librustzcash to >= 1.0, < 2.0 (or at least < 1.11), then enable zcash_primitives/test-dependencies in Zebra's proptest-impl feature. This unblocks orchard::bundle::testing.
2. Add a minimal orchard bundle builder to Zebra's test code that constructs bundles using only the public orchard::Bundle::from_parts API with dummy/zero values (if the orchard crate exposes enough public constructors).
3. Wait for the orchard crate to add public test helpers that don't require the test-dependencies feature.

Option 1 is the simplest and most complete fix.

Related: #10462 (original tracking discussion, now mostly resolved)