Cardano Updates

The URL <https://...> in the ADR file was being interpreted as JSX by MDX,
causing a build failure in the docs site. Replaced with a proper markdown link.

Signed-off-by: Pat Losoponkul <[email protected]>

- shared-consensus/praos.rs: drop unused `let now` in equivocation test
- sim-core/clock/coordinator.rs: `while let Poll::Pending = poll!(...)`
  -> `while poll!(...).is_pending()`
- sim-core/sim/shared_consensus.rs: drop redundant `as u64` cast on
  `rb_win_threshold` (already returns u64)
- sim-core/sim/shared_consensus.rs: collapse `contains_key + insert`
  into `entry(id).or_insert(...)` in `receive_announce_eb`

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Move the sans-IO consensus crate from /con-rs/ to /shared-rs/consensus/
under a new top-level Cargo workspace mirroring the layout already on
prc/tcp-model, so consumer-neutral crates can sit alongside without
either net-rs or sim-rs depending on each other.

- Crate name con-rs -> shared-consensus; LeiosVariant::ConRs ->
  SharedConsensus (YAML key "shared-consensus"); adapter module
  sim-rs/sim-core/src/sim/con_rs.rs -> shared_consensus.rs.
- All con_rs:: paths in sim-rs and net-rs sources updated to
  shared_consensus::; Cargo.toml dependency paths updated to
  ../../shared-rs/consensus.
- CLAUDE.md, README.md, config.schema.json descriptions, and merge
  plan doc retitled to reflect the new name; doc comments inside the
  crate switched to consumer-neutral phrasing where they self-named.
- shared-rs/Cargo.lock replaces the per-crate lockfile; sim-rs and
  net-rs lockfiles regenerated.

Builds: shared-rs (238 tests), net-rs (119 tests), sim-rs (55 tests).
Clippy: shared-rs and sim-rs each have pre-existing lints unrelated
to this move; net-rs is clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>