feat(dao): scaffold aldabra-dao crate (Phase 1 reads)

Adds a 4th workspace crate `aldabra-dao` for native Agora-on-Cardano
DAO interaction. Multi-DAO from day one — DaoConfig per DAO at
\$ALDABRA_DATA/daos/<name>.json + .active selector. Sulkta DAO and any
community Agora deployment (Bob's DAO, Alice's DAO) are first-class.

Phase 0 type port complete:
- StakeDatum, StakeRedeemer, ProposalAction, ProposalLock, Credential
- ProposalDatum, ProposalRedeemer, ProposalStatus, ProposalThresholds,
  ProposalTimingConfig, ProposalVotes
- GovernorDatum, GovernorRedeemer
- All Constr indices verified against Agora source makeIsDataIndexed
  + EnumIsData declarations (Stake/Proposal/Governor/Action/Status all
  cross-referenced)
- Round-trip tests for every type

Phase 1 read surface (this commit):
- DaoStore: DaoConfig load/save/list/remove + active-DAO selector with
  first-register-becomes-active UX. 8 unit tests.
- DaoReader trait + KoiosDaoReader impl for get_governor + list_stakes.
  list_proposals stubbed pending Phase 4 proposal-script-address discovery.
- Stake address sharing handled: list_stakes filters on gov_token_policy
  (the shared MLabs stakes addr serves many DAOs).

Stubs for upcoming phases:
- agora/treasury.rs (Phase 4 — treasury spend helpers)
- agora/authority_token.rs (Phase 4 — GAT mint/burn)
- agora/reference_scripts.rs (Phase 2/3 — independent script-hash discovery
  per Sulkta's choice 2026-05-05; computed locally, never trust MLabs registry)
- builder/mod.rs (per-operation Plutus tx builders, populated phase-by-phase)

Spec doc + decisions: internal notes in workspace.

Effects map (`ProposalDatum.effects`) kept as raw PlutusData for round-trip
integrity until Phase 4 (proposal create) needs typed access.

ExUnits strategy locked: Koios tx_evaluate from day one (no hardcoded values).
Wired up in Phase 2 alongside reference-script discovery.

crates/aldabra-dao/src/lib.rs

@@ -0,0 +1,35 @@
+//! aldabra-dao — Agora-on-Cardano DAO interaction.
+//!
+//! Native client for any [Agora](https://github.com/Liqwid-Labs/agora)
+//! deployment on Cardano. Multi-DAO from day one — Sulkta DAO, Bob's
+//! DAO, and Alice's DAO are all first-class, configured per-instance
+//! at `$ALDABRA_DATA/daos/<name>.json`.
+//!
+//! ## Surface
+//!
+//! - [`config`] — per-DAO config files + active-DAO selector.
+//! - [`agora`] — Plutarch datum/redeemer type ports with PlutusData
+//!   encode/decode.
+//! - [`reader`] — Koios-backed state queries (governor, stakes,
+//!   proposals).
+//! - [`builder`] — Plutus tx assembly per operation (stake_create,
+//!   proposal_vote, etc).
+//! - [`error::DaoError`] — crate-internal error type.
+//!
+//! ## What this crate is NOT
+//!
+//! - Not a key store. Signing is delegated to `aldabra-core`.
+//! - Not an MCP server. The `dao_*` tools that wrap these primitives
+//!   live in `aldabra-mcp`.
+//! - Not Sulkta-specific. Every Sulkta value (TRP policy, governor
+//!   address, etc) comes from a [`config::DaoConfig`] loaded at
+//!   runtime, never compile-time.
+
+pub mod agora;
+pub mod builder;
+pub mod config;
+pub mod error;
+pub mod reader;
+
+pub use config::{ActiveDao, DaoConfig, DaoStore};
+pub use error::DaoError;