feat: per-channel responsePrefix override (#9001)

* feat: per-channel responsePrefix override

Add responsePrefix field to all channel config types and Zod schemas,
enabling per-channel and per-account outbound response prefix overrides.

Resolution cascade (most specific wins):
  L1: channels.<ch>.accounts.<id>.responsePrefix
  L2: channels.<ch>.responsePrefix
  L3: (reserved for channels.defaults)
  L4: messages.responsePrefix (existing global)

Semantics:
  - undefined -> inherit from parent level
  - empty string -> explicitly no prefix (stops cascade)
  - "auto" -> derive [identity.name] from routed agent

Changes:
  - Core logic: resolveResponsePrefix() in identity.ts accepts
    optional channel/accountId and walks the cascade
  - resolveEffectiveMessagesConfig() passes channel context through
  - Types: responsePrefix added to WhatsApp, Telegram, Discord, Slack,
    Signal, iMessage, Google Chat, MS Teams, Feishu, BlueBubbles configs
  - Zod schemas: responsePrefix added for config validation
  - All channel handlers wired: telegram, discord, slack, signal,
    imessage, line, heartbeat runner, route-reply, native commands
  - 23 new tests covering backward compat, channel/account levels,
    full cascade, auto keyword, empty string stops, unknown fallthrough

Fully backward compatible - no existing config is affected.
Fixes #8857

* fix: address CI lint + review feedback

- Replace Record<string, any> with proper typed helpers (no-explicit-any)
- Add curly braces to single-line if returns (eslint curly)
- Fix JSDoc: 'Per-channel' → 'channel/account' on shared config types
- Extract getChannelConfig() helper for type-safe dynamic key access

* fix: finish responsePrefix overrides (#9001) (thanks @mudrii)

* fix: normalize prefix wiring and types (#9001) (thanks @mudrii)

---------

Co-authored-by: Gustavo Madeira Santana <gumadeiras@gmail.com>

src/config/zod-schema.providers-core.ts

@@ -137,6 +137,7 @@ export const TelegramAccountSchemaBase = z
     reactionLevel: z.enum(["off", "ack", "minimal", "extensive"]).optional(),
     heartbeat: ChannelHeartbeatVisibilitySchema,
     linkPreview: z.boolean().optional(),
+    responsePrefix: z.string().optional(),
   })
   .strict();
 
@@ -321,6 +322,7 @@ export const DiscordAccountSchema = z
       })
       .strict()
       .optional(),
+    responsePrefix: z.string().optional(),
   })
   .strict();
 
@@ -391,6 +393,7 @@ export const GoogleChatAccountSchema = z
       .optional(),
     dm: GoogleChatDmSchema.optional(),
     typingIndicator: z.enum(["none", "message", "reaction"]).optional(),
+    responsePrefix: z.string().optional(),
   })
   .strict();
 
@@ -505,6 +508,7 @@ export const SlackAccountSchema = z
     dm: SlackDmSchema.optional(),
     channels: z.record(z.string(), SlackChannelSchema.optional()).optional(),
     heartbeat: ChannelHeartbeatVisibilitySchema,
+    responsePrefix: z.string().optional(),
   })
   .strict();
 
@@ -588,6 +592,7 @@ export const SignalAccountSchemaBase = z
       .optional(),
     reactionLevel: z.enum(["off", "ack", "minimal", "extensive"]).optional(),
     heartbeat: ChannelHeartbeatVisibilitySchema,
+    responsePrefix: z.string().optional(),
   })
   .strict();
 
@@ -652,6 +657,7 @@ export const IMessageAccountSchemaBase = z
       )
       .optional(),
     heartbeat: ChannelHeartbeatVisibilitySchema,
+    responsePrefix: z.string().optional(),
   })
   .strict();
 
@@ -731,6 +737,7 @@ export const BlueBubblesAccountSchemaBase = z
     blockStreamingCoalesce: BlockStreamingCoalesceSchema.optional(),
     groups: z.record(z.string(), BlueBubblesGroupConfigSchema.optional()).optional(),
     heartbeat: ChannelHeartbeatVisibilitySchema,
+    responsePrefix: z.string().optional(),
   })
   .strict();
 
@@ -813,6 +820,7 @@ export const MSTeamsConfigSchema = z
     /** SharePoint site ID for file uploads in group chats/channels (e.g., "contoso.sharepoint.com,guid1,guid2") */
     sharePointSiteId: z.string().optional(),
     heartbeat: ChannelHeartbeatVisibilitySchema,
+    responsePrefix: z.string().optional(),
   })
   .strict()
   .superRefine((value, ctx) => {