feat: share repeated projection material in application contracts

[patrickleet]

Applications retaining several generations of event selectors repeat identical operation lists and body schemas for every projection arm. Forge's complete typed manifest crosses the existing 4 MiB cap even though the authoring DSL already shares mutations.

Emit shared_projection_program_v1 in modeled application-contract data only when it is smaller than the expanded form. Canonical tables share complete operation arrays and exact schema strings; every arm ID, selector identity/version, expression, ordering and effect is retained. expand_projection_program_contract accepts both encodings and reconstructs the original JSON. Validation rejects invalid references, ambiguous inline data, noncanonical/unused table entries and excessive expansion before cloning shared values.

Runtime projection IR, program/binding IDs, execution and client projection-program exports remain unchanged. Old expanded artifacts remain readable and byte-stable. Newly shared Surface artifact fingerprints change deterministically; rebuild service/client artifacts together. The complete wire cap stays 4,194,304 bytes and each opaque value/expanded program remains bounded at 1 MiB.

Forge validation at 7cc8f71b6a494da30f785b4933add6d6d853be73, using a Cargo dependency override with no Forge edits:

Complete artifact	Bytes
Losslessly expanded equivalent	4,234,915
Compact canonical manifest	3,225,789
Saved	1,009,126

The expanded equivalent contains exactly the same decoded program data; Rust JSON serialization measured both sizes without numeric conversion. Both previously failing full/authorized-content manifest tests now pass.

Validation:

• cargo test --all-features --lib: 1,080 passed, 4 ignored.
• Application composition/plans integration: 35 passed.
• Full distributed_cli suite: 293 passed, 11 ignored; explicitly enabled CLI manifest integration: 6 passed.
• Forge GraphQL suite: 43 passed, 4 ignored.
• Forge projections suite: 42 passed, including retained v2/v3 events and current/retained lifecycle equivalence.
• Five new tests cover exact 32-selector round trips, stable expanded encoding, full-manifest size/fingerprints, malformed references and bounded expansion.
• Changed Rust formatting and git diff --check pass.

Stacked on #248; the change introduces no historical-selector omission, replay exemption, Forge workaround or cap increase.

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