fix(instagram): read the user timeline the web client loads

[Benjamin-eecs]

Description

instagram user is dead for every account. Instagram retired /api/v1/feed/user/* for web sessions: it answers 200 with redirected: true and the homepage app shell, so this command's if (!r2.ok) guard cannot fire and r2.json() throws a raw SyntaxError under the UNKNOWN code. Its documented fallback is gone too, web_profile_info answers 429 with an HTML block page (#2456).

The command now reads the timeline the web client itself loads: it forces a fresh document, installs the request interceptor, routes to the profile through the history API so the interceptor survives, drains captures until the timeline arrives, and scrolls when the limit needs another page. Instagram's own Relay client issues the query, so nothing here pins a persisted-query doc_id.

Related issue: Closes #2456

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🌐 New site adapter
• 📝 Documentation
• ♻️ Refactor
• 🔧 CI / build / tooling

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Documentation (if adding/modifying an adapter)

• Added doc page under docs/adapters/ (if new adapter)
• Updated docs/adapters/index.md table (if new adapter)
• Updated sidebar in docs/.vitepress/config.mts (if new adapter)
• Updated README.md / README.zh-CN.md when command discoverability changed
• Used positional args for the command's primary subject unless a named flag is clearly better
• Normalized expected adapter failures to CliError subclasses instead of raw Error

Screenshots / Output

Both endpoints, probed in a logged-in session:

feed/user/natgeo/username/   200  redirected:true  finalUrl:https://www.instagram.com/  text/html
web_profile_info?username=   429  text/html (block page)

Before, on any account:

$ opencli instagram user natgeo --limit 3
ok: false
error:
  code: UNKNOWN
  message: 'SyntaxError: Unexpected token ''<'', "<!DOCTYPE "... is not valid JSON'
  exitCode: 1
# AutoFix: re-run with --trace=retain-on-failure for trace artifact
# opencli instagram user --trace retain-on-failure

After, same session (first of three rows):

$ opencli instagram user natgeo --limit 3
- index: 1
  caption: 'Presented by @Rolex. Welcome to Africa 🌍 Africa Earth’s Wild Home takes you deep into the heart of '
  likes: 69973
  comments: 405
  type: video
  date: 9/10/2026

--limit 20 returns 20 distinct posts across captured pages, a professional account resolves the same way, and a handle with no public timeline reports COMMAND_EXEC naming the cause instead of leaking a page stack trace. clis/instagram suite 204 / 204, and every behaviour above is mutation-checked: reverting any one of the forced reload, the envelope unwrap, the settled-pathname check, the pagination gates, deduplication, media id or media type validation, capture-timeout classification or deferred GraphQL error reporting fails a test. Typecheck, both lint gates and doc coverage pass; cli-manifest.json changes only this command's strategy and navigateBefore entries.

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