[Backport M106] chore: Add CLI workflow for Cody release captains (#8091)

Creates an interactive script to guide release captains through the
complete Cody release process.

Note: This is just an initial PR. I might have more PRs to improve the
script later.

## Test plan
./release/release-captain.sh
![Screenshot 2025-06-18 at 6 09
53 PM](https://github.com/user-attachments/assets/bfb55b35-7a1c-442d-b20f-1510e3764849)



 <br> Backport 3407254 from #8078

Co-authored-by: julialeex <julia.xu@sourcegraph.com>

Author: sourcegraph-release-bot

release/README.md

@@ -0,0 +1,106 @@
+# Cody Release Captain CLI
+
+This directory contains automation scripts for Cody release captains.
+
+## release-captain.sh
+
+An interactive CLI workflow that follows the [Release Captain Playbook](https://www.notion.so/sourcegraph/Release-Captain-Playbook-13ba8e112658800d877ce7b4e8413935) and guides release captains through the complete Cody release process.
+
+### Prerequisites
+
+- Git CLI
+- GitHub CLI (`gh`)
+- `jq` for JSON processing
+- Write access to the Cody repository
+- JetBrains account with admin access (for JetBrains releases)
+- `GITHUB_TOKEN` environment variable set
+
+### Usage
+
+```bash
+./release/release-captain.sh
+```
+
+The script provides an interactive menu with these options:
+
+1. **Day 1: Create release branch** - Creates release branch, backport labels, and prerelease builds
+2. **Day 2-6: Stabilize release branch** - Helps create new prerelease builds after backports
+3. **Day 7: Ship stable release** - Guides through stable release process for VSCode, JetBrains, and Agent
+4. **Emergency patch release** - Creates emergency patch releases when needed
+5. **Check prerequisites** - Validates required tools and permissions
+
+### Environment Variables
+
+- `MILESTONE` - The milestone number (e.g., 66). If not set, the script will prompt for it.
+
+### Example
+
+```bash
+# Set milestone and run
+export MILESTONE=66
+./release/release-captain.sh
+```
+
+### Manual Steps Still Required
+
+The script automates most tasks but still requires manual steps for:
+
+- Reviewing and organizing generated changelogs
+- JetBrains Marketplace management (unhiding releases, writing release notes)
+- Community notifications and QA coordination
+- Monitoring workflow statuses
+- Final release verification
+
+### Copy-Paste Templates
+
+#### 1. Notify #team-cody-core (Day 1)
+
+```text
+Hey team! 👋 I'm the release captain for milestone {MILESTONE}.
+
+We've branched from commit {COMMIT_HASH} for M{MILESTONE}, which will produce:
+- VSCode v1.{MILESTONE}.0 
+- JetBrains v7.{MILESTONE}.0
+
+**For ship-blocking fixes**: Add the `backport M{MILESTONE}` label to your PRs.
+
+**Prerelease versions for dogfooding**:
+- VSCode Insiders: v1.{MILESTONE_MINUS_ONE}.{BUILD} 
+- JetBrains Nightly: v7.{MILESTONE_MINUS_ONE}.0-nightly
+
+Please update your extensions and help us test! 🧪
+
+Next opportunity to reach stable: land code by {NEXT_BRANCH_DATE}, ships {NEXT_RELEASE_DATE}.
+```
+
+#### 2. Request QA (#ext-qa-fibilabs-sourcegraph)
+
+```text
+Hi QA team! 👋
+
+New prerelease builds are ready for testing:
+- **JetBrains**: v7.{MILESTONE_MINUS_ONE}.0-nightly
+- **VSCode Insiders**: v1.{MILESTONE_MINUS_ONE}.{BUILD}
+
+Please QA these versions and report any issues. Thanks! 🙏
+```
+
+#### 3. Introduce to Community Support (#discuss-community-support)
+
+```text
+Hi community support team! 👋
+
+I'm the release captain for Cody milestone {MILESTONE}. 
+
+**Current prerelease versions**:
+- VSCode Insiders: v1.{MILESTONE_MINUS_ONE}.{BUILD}
+- JetBrains Nightly: v7.{MILESTONE_MINUS_ONE}.0-nightly
+
+Please flag any issues you see with these versions - especially helpful since prerelease has fewer users. Thanks for the partnership! 🤝
+```
+
+### Related Documentation
+
+- Main release guide: See the comprehensive release captain guide in the codebase
+- [Agent release guide](../agent/README.md#updating-the-polly-http-recordings)
+- [Cody Web publishing guide](../web/publish.md)