fix: Discord Ed25519 signature verification and capabilities header alias (#148) (#372)

* test: add failing tests for Discord signature validation and capabilities alias (Red phase)

TDD Red phase for #148. Adds 19 tests across 4 categories:
- Category 1: CredentialLocationSchema header_name alias (2 failing)
- Category 2: Ed25519 signature verification (3 failing)
- Category 3: Router signature key management (2 failing)
- Category 5: Discord capabilities public_key setup (1 failing)

All 8 failures are expected — stubs return false/None by design.
Implementation will follow in Green phase.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: add Discord Ed25519 signature verification and capabilities alias (#148)

Implement the Green phase for Discord channel security fixes:

- Add real Ed25519 signature verification in signature.rs using ed25519-dalek
- Add #[serde(alias = "header_name")] to CredentialLocationSchema::Header
  for backward compatibility with external JSON files
- Add signature_keys storage to WasmChannelRouter (register/get/unregister)
- Add discord_public_key to discord.capabilities.json setup.required_secrets
- Add nested capabilities resolution to CapabilitiesFile for channel-level
  JSON compatibility

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* style: address PR #372 review comments

- Fix invalid hex character in test fake_pub_key (router.rs)
- Simplify signature parsing with from_slice/try_from (signature.rs)
- Use idiomatic Option::or for nested capability merging (capabilities_schema.rs)

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: enforce signature verification, staleness check, key validation, recursive resolve

Address PR #372 review feedback:

- Wire verify_discord_signature() into webhook_handler with Ed25519
  signature + timestamp staleness check (5s window via now_secs param)
- Validate Ed25519 keys in register_signature_key() (hex decode +
  VerifyingKey::try_from) before storing, return Result<(), String>
- Recursively resolve nested capabilities in resolve_nested()
- Add 25 new tests: 8 staleness, 6 key validation, 7 webhook
  integration (tower::oneshot), 4 resolve_nested edge cases
- Fix pre-existing clippy warning in signal.rs

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: wire register_signature_key() into all channel loading paths

The Ed25519 signature key registration was implemented and tested but
never called from production code. All three channel loading paths
(setup_wasm_channels, activate_wasm_channel, refresh_active_channel)
now read the public key from the secrets store and register it with
the webhook router, enabling Discord signature verification.

Adds `signature_key_secret_name` field to WebhookSchema so channels
can declare which secret contains their Ed25519 public key.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

Cargo.lock

@@ -492,6 +492,12 @@ version = "0.22.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
 
+[[package]]
+name = "base64ct"
+version = "1.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2af50177e190e07a26ab74f8b1efbfe2ef87da2116221318cb1c2e82baf7de06"
+
 [[package]]
 name = "bincode"
 version = "1.3.3"
@@ -949,6 +955,12 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "const-oid"
+version = "0.9.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2459377285ad874054d797f3ccebf984978aa39129f6eafde5cdc8315b612f8"
+
 [[package]]
 name = "const-random"
 version = "0.1.18"
@@ -1353,6 +1365,33 @@ dependencies = [
  "cipher",
 ]
 
+[[package]]
+name = "curve25519-dalek"
+version = "4.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "97fb8b7c4503de7d6ae7b42ab72a5a59857b4c937ec27a3d4539dba95b5ab2be"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "curve25519-dalek-derive",
+ "digest",
+ "fiat-crypto",
+ "rustc_version",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "curve25519-dalek-derive"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f46882e17999c6cc590af592290432be3bce0428cb0d5f8b6715e4dc7b383eb3"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.116",
+]
+
 [[package]]
 name = "darling"
 version = "0.21.3"
@@ -1438,6 +1477,16 @@ dependencies = [
  "uuid",
 ]
 
+[[package]]
+name = "der"
+version = "0.7.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e7c1832837b905bbfb5101e07cc24c8deddf52f93225eee6ead5f4d63d53ddcb"
+dependencies = [
+ "const-oid",
+ "zeroize",
+]
+
 [[package]]
 name = "deranged"
 version = "0.5.6"
@@ -1607,6 +1656,30 @@ version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d0881ea181b1df73ff77ffaaf9c7544ecc11e82fba9b5f27b262a3c73a332555"
 
+[[package]]
+name = "ed25519"
+version = "2.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "115531babc129696a58c64a4fef0a8bf9e9698629fb97e9e40767d235cfbcd53"
+dependencies = [
+ "pkcs8",
+ "signature",
+]
+
+[[package]]
+name = "ed25519-dalek"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70e796c081cee67dc755e1a36a0a172b897fab85fc3f6bc48307991f64e4eca9"
+dependencies = [
+ "curve25519-dalek",
+ "ed25519",
+ "serde",
+ "sha2",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "ego-tree"
 version = "0.10.0"
@@ -1773,6 +1846,12 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "fiat-crypto"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28dea519a9695b9977216879a3ebfddf92f1c08c05d984f8996aecd6ecdc811d"
+
 [[package]]
 name = "filetime"
 version = "0.2.27"
@@ -2719,9 +2798,11 @@ dependencies = [
  "deadpool-postgres",
  "dirs 6.0.0",
  "dotenvy",
+ "ed25519-dalek",
  "flate2",
  "fs4",
  "futures",
+ "hex",
  "hkdf",
  "html-to-markdown-rs",
  "http-body-util",
@@ -3814,6 +3895,16 @@ dependencies = [
  "futures-io",
 ]
 
+[[package]]
+name = "pkcs8"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f950b2377845cebe5cf8b5165cb3cc1a5e0fa5cfa3e1f7f55707d8fd82e0a7b7"
+dependencies = [
+ "der",
+ "spki",
+]
+
 [[package]]
 name = "pkg-config"
 version = "0.3.32"
@@ -5104,6 +5195,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "signature"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77549399552de45a898a580c1b41d445bf730df867cc44e6c0233bbc4b8329de"
+dependencies = [
+ "rand_core 0.6.4",
+]
+
 [[package]]
 name = "simd-adler32"
 version = "0.3.8"
@@ -5157,6 +5257,16 @@ dependencies = [
  "windows-sys 0.60.2",
 ]
 
+[[package]]
+name = "spki"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d91ed6c858b01f942cd56b37a94b3e0a1798290327d1236e4d9cf4eaca44d29d"
+dependencies = [
+ "base64ct",
+ "der",
+]
+
 [[package]]
 name = "sptr"
 version = "0.3.2"