feat(web-api): add code_channels app manifest feature

[zimeg]

Summary

This pull request adds the code_channels app manifest feature to the hand-maintained manifest types in @slack/web-api (used by the apps.manifest.* methods), mirroring slackapi/manifest-schema and the Slack CLI (slackapi/slack-cli#641).

• Adds features.code_channels with the optional enabled and slash_command_url fields. Descriptions are taken from the manifest schema.
• Adds the code_channels:manage scope to the bot scopes, which the agents.conversations.* methods require.
• Extends the apps.test-d.ts tsd coverage with a happy path for the new feature and scope, and a sad path for a non-boolean enabled.

Reference: Enabling code channels.

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: cae703c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@slack/web-api	Minor

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.38%. Comparing base (2f5954b) to head (cae703c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2776   +/-   ##
=======================================
  Coverage   89.38%   89.38%           
=======================================
  Files          65       65           
  Lines       10525    10525           
  Branches      478      478           
=======================================
  Hits         9408     9408           
  Misses       1086     1086           
  Partials       31       31           

Flag	Coverage Δ
cli-hooks	89.32% <ø> (ø)
cli-test	89.32% <ø> (ø)
logger	89.32% <ø> (ø)
oauth	89.32% <ø> (ø)
socket-mode	89.32% <ø> (ø)
web-api	89.32% <ø> (ø)
webhook	89.32% <ø> (ø)

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