fix(skills): bump @chat-adapter/* cohort to 4.27.0

@chat-adapter/discord@4.27.0 includes vercel/chat#256, which fixes the
Discord adapter unconditionally setting payload.content alongside
payload.embeds when posting a card. In 4.26.0 every Discord card
appeared twice (text content above the embed, identical content inside
the embed) — every new install reproduced this on the welcome tour and
on every approval card.

The other 7 skills bump in lockstep because @chat-adapter/discord@4.27.0
depends on chat@4.27.0 while @chat-adapter/<other>@4.26.0 depend on
chat@4.26.0. Mixing the cohort produces a TypeScript dual-version
conflict between the bridge and adapter ChatInstance types.

Files updated (one line per file in each pnpm install command):
- add-discord (the user-visible bug fix)
- add-gchat, add-github, add-linear, add-slack, add-teams, add-telegram,
  add-whatsapp-cloud (cohort consistency)

Out of scope: add-imessage, add-matrix, add-webex, add-resend use
third-party packages with independent versioning.

Closes #2264

.claude/skills/add-discord/SKILL.md

@@ -44,7 +44,7 @@ import './discord.js';
 ### 4. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/discord@4.26.0
+pnpm install @chat-adapter/discord@4.27.0
 ```
 
 ### 5. Build

.claude/skills/add-gchat/SKILL.md

@@ -44,7 +44,7 @@ import './gchat.js';
 ### 4. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/gchat@4.26.0
+pnpm install @chat-adapter/gchat@4.27.0
 ```
 
 ### 5. Build

.claude/skills/add-github/SKILL.md

@@ -48,7 +48,7 @@ import './github.js';
 ### 4. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/github@4.26.0
+pnpm install @chat-adapter/github@4.27.0
 ```
 
 ### 5. Build

.claude/skills/add-linear/SKILL.md

@@ -87,7 +87,7 @@ Linear OAuth apps can't be @-mentioned, so the bridge's `onNewMention` handler n
 ### 5. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/linear@4.26.0
+pnpm install @chat-adapter/linear@4.27.0
 ```
 
 ### 6. Build

.claude/skills/add-slack/SKILL.md

@@ -44,7 +44,7 @@ import './slack.js';
 ### 4. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/slack@4.26.0
+pnpm install @chat-adapter/slack@4.27.0
 ```
 
 ### 5. Build

.claude/skills/add-teams/SKILL.md

@@ -44,7 +44,7 @@ import './teams.js';
 ### 4. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/teams@4.26.0
+pnpm install @chat-adapter/teams@4.27.0
 ```
 
 ### 5. Build

.claude/skills/add-telegram/SKILL.md

@@ -58,7 +58,7 @@ In `setup/index.ts`, add this entry to the `STEPS` map (right after the `registe
 ### 5. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/telegram@4.26.0
+pnpm install @chat-adapter/telegram@4.27.0
 ```
 
 ### 6. Build

.claude/skills/add-whatsapp-cloud/SKILL.md

@@ -44,7 +44,7 @@ import './whatsapp-cloud.js';
 ### 4. Install the adapter package (pinned)
 
 ```bash
-pnpm install @chat-adapter/whatsapp@4.26.0
+pnpm install @chat-adapter/whatsapp@4.27.0
 ```
 
 ### 5. Build