[ElizabethChi]

closes #762

What's actually going on

The "Clippy Lint" job in .github/workflows/ci.yml already runs:

cargo clippy --all-targets --all-features -- -D warnings -D clippy::all -D clippy::pedantic

So pedantic clippy and warnings-as-errors is already enabled in CI config. The problem is the check currently can't finish: share-math fails to compile under clippy::all itself (not just a pedantic nit), and once that's past, the main vault crate has 3 real compile errors that block clippy from reaching the pedantic lint pass at all.

Fixes

• share-math/src/queue.rs: chunks_exact(4) triggers clippy::chunks_exact_to_as_chunks, which -D clippy::all makes a hard error. Switched to as_chunks::<4>() (stable since Rust 1.88, no nightly feature needed).
• lib.rs: a panic path referenced VaultError::DepositRejectedZeroAssetsWithShares (added for security(contract): convert_to_shares mints 1:1 when TotalShares > 0 but TotalAssets == 0 #973's zero-assets-with-shares protection), but the variant was never added to the enum. Added it at the next free discriminant (93).
• test_zero_assets_with_shares.rs: both should_panic(expected = "Error(Contract, #86)") assertions were asserting the wrong code (Reject negative cap values in all limit setters #86 is InvalidRateLimitConfig, unrelated). Updated to #93 to match the variant above. Also fixed entries.push(...) to entries.push_back(...) in the same file (soroban_sdk::Vec has no push method), a separate pre-existing compile error in the same test.
• lib.rs: removed two needless mut bindings that -D warnings promotes to hard errors.

Disclosure

With those 3 compile errors fixed, clippy runs to completion on the vault crate and surfaces 371 real clippy::pedantic findings (182 pass-by-value params, 75 missing #[must_use], 57 missing doc backticks, plus smaller categories: casts expressible via From, functions over the line-length lint, etc.). That's a large, separate cleanup effort, not something this PR attempts. The issue's literal scope (enabling the check) is already done in CI config; what was missing was just getting the build to a state where the check can run.

Also confirmed but not touched here (separate, unrelated to #762):

• cargo test --all-targets still fails to compile on a fresh clone of main (about a dozen errors, mostly test call sites passing an extra owner/auth argument to vault setters like set_max_decrease_bps/set_min_holding_period whose current signatures don't take one, plus a missing Ledger::set_sequence).
• cargo fmt --all -- --check has pre-existing unrelated drift in tests/mod.rs (alphabetical mod ordering), present on a clean clone of main too.

Verified: cargo clippy -p share-math --all-features -- -D warnings -D clippy::all -D clippy::pedantic is now fully clean. cargo clippy --all-features (lib only, not --all-targets) on the vault crate now compiles and runs to completion (371 pedantic findings, down from "doesn't compile").