refactor: remove code that no production path reaches

These were all scaffolding that drifted out of use, and each one costs
a reader time before they discover it does nothing:

- UUIDASStringSerializer duplicated UUIDSerializer byte for byte; the
  differing descriptor name never reaches the JSON/YAML wire format, so
  the choice between them was a coin flip for contributors.
- Velocity's BuildInfo was never referenced (the plugin reads its version
  from PluginContainer) and read a "commit" property the build never
  wrote, so it would have reported "unknown" had anyone called it.
- KanaConverter.TrieNode.Leaf is never constructed: buildTrie starts from
  a Branch and insert only ever returns Branch. Six branches guarded
  against a state the type system allowed but the code could not produce.
  With those gone, isValidRomaji and toHiragana were visibly the same
  trie walk, so they now share one longestMatch.
- @Deprecated command handling had no annotated command to act on.
- The settings backup restore looked for *.backup.* files that nothing in
  the repository writes, so it always fell through to empty settings.

Also drops CommandContext.replyWithEvent/replyPlain, PluginCoroutineScope's
unused plugin parameter, GitHubRelease fields no caller reads, and four
language keys with no lookup site.

Co-Authored-By: Claude <noreply@anthropic.com>

3 files changed, 0 insertions, 29 deletions

diff --git a/platform-velocity/build.gradle.kts b/platform-velocity/build.gradle.kts
index 3cd8c2d..65bd27f 100644
--- a/platform-velocity/build.gradle.kts
+++ b/platform-velocity/build.gradle.kts
@@ -57,9 +57,6 @@ tasks {
         filesMatching("velocity-plugin.json") {
             expand(props)
         }
-        filesMatching("build-info.properties") {
-            expand(props)
-        }
     }
 
     build {
diff --git a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/BuildInfo.kt b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/BuildInfo.kt
deleted file mode 100644
index 1cb13d4..0000000
--- a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/BuildInfo.kt
+++ /dev/null
@@ -1,23 +0,0 @@
-package dev.m1sk9.lunaticChat.velocity
-
-import java.util.Properties
-
-object BuildInfo {
-    val version: String
-    val commitHash: String
-    val channel: String
-
-    init {
-        val props = Properties()
-        BuildInfo::class.java.getResourceAsStream("/build-info.properties")?.use {
-            props.load(it)
-        }
-        version = props.getProperty("version", "unknown")
-        commitHash = props.getProperty("commit", "unknown")
-        channel = props.getProperty("channel", "stable")
-    }
-
-    val isNightly: Boolean get() = channel == "nightly"
-
-    fun versionWithCommit(): String = "$version ($commitHash)"
-}
diff --git a/platform-velocity/src/main/resources/build-info.properties b/platform-velocity/src/main/resources/build-info.properties
deleted file mode 100644
index 1f8dbc2..0000000
--- a/platform-velocity/src/main/resources/build-info.properties
+++ /dev/null
@@ -1,3 +0,0 @@
-version=${version}
-commit=${gitCommitHash}
-channel=${channel}