feat(core): add compat.rs re-export layer for platform SDK types (#19)

* feat(core): add compat.rs re-export layer for platform SDK types

Create new term-core crate with src/core/compat.rs providing:
- Re-exports of Hotkey, ChallengeId (UUID-based) from platform_core
- Re-exports of WeightAssignment, ChallengeRoute (HttpMethod enum),
  RouteRequest, RouteResponse, ChallengeError, ServerChallenge from
  platform_challenge_sdk
- ChallengeConfigMeta thin wrapper combining metadata + config
- Deprecated backward-compatible aliases (LegacyChallengeId,
  LegacyWeightAssignment, LegacyRoute) with Into conversions
- Conversion utilities (weight_u16_to_f64, challenge_id_from_bytes,
  method_str_to_enum, normalize_weights, etc.)
- Prelude submodule for convenient imports
- 153 tests (126 unit + 27 doc tests)

* fix: use git deps for core crate instead of local paths

* fix: resolve sled lock contention in chain storage test

Author: echobt

Cargo.lock

@@ -1,6 +1,6 @@
 [workspace]
 resolver = "2"
-members = [".", "wasm", "cli", "server", "storage"]
+members = [".", "wasm", "cli", "core", "server", "storage"]
 default-members = ["wasm"]
 
 [workspace.package]

Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "term-core"
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+description = "Core compatibility layer — re-exports platform SDK types for term-challenge"
+
+[dependencies]
+platform-core = { git = "https://github.com/PlatformNetwork/platform-v2", branch = "main" }
+platform-challenge-sdk = { git = "https://github.com/PlatformNetwork/platform-v2", branch = "main" }
+
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+uuid = { version = "1", features = ["v4"] }
+chrono = { version = "0.4", features = ["serde"] }
+async-trait = "0.1"
+thiserror = "1.0"
+
+[dev-dependencies]
+tokio = { version = "1.40", features = ["rt", "macros"] }