AI Chat: Remove Claude Instant model in favor of Claude Haiku and Claude Sonnet

[petemill]

Also removes version (date) from model name, since server uses latest configured.

Resolves brave/brave-browser#37988

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

• Not premium user
• Using a version before this commit, set Claude Instant to be the default
• Verify every new conversation uses Claude Instant
• Quit the browser and open again using this commit, with the same profile
• Verify that every new conversation uses Claude Haiku
• Repeat for premium user except every new conversation should now use Claude Sonnet

[github-actions]

_{reported by reviewdog 🐶}
[semgrep] base::Unretained is most of the time unrequited, and a weak reference is better suited for secure coding.
Consider swapping Unretained for a weak reference.
base::Unretained usage may be acceptable when a callback owner is guaranteed
to be destroyed with the object base::Unretained is pointing to, for example:

- PrefChangeRegistrar
- base::*Timer
- mojo::Receiver
- any other class member destroyed when the class is deallocated


Source: https://github.com/brave/security-action/blob/main/assets/semgrep_rules/client/chromium-uaf.yaml


Cc @thypon @goodov @iefremov

[LorenzoMinto]

Should we also address brave/brave-browser#38071 and brave/brave-browser#38195 in this PR? Should be a minimal addition.

[petemill]

Should we also address brave/brave-browser#38071 and brave/brave-browser#38195 in this PR? Should be a minimal addition.

The server-side doesn't seem ready for that, so I'd prefer to keep them separate. Also the QA work for this is larger, so would like to allow them to get started verifying instead of waiting.

[stephendonner]

Verification PASSED using

Brave | 1.68.64 Chromium: 126.0.6478.26 (Official Build) nightly (64-bit)
-- | --
Revision | d9689f56dafd3c9d8622461f6b4864053b0706aa
OS | Windows 10 Version 22H2 (Build 19045.4474)

New profiles, default (Mixtral) - PASSED

Steps:

1. install 1.68.64
2. launch Brave using --enable-features=AIChat:conversation_api\true --env-leo=staging --env-ai-chat.bsg=dev --env-ai-chat-premium.bsg=dev
3. opened brave://settings/leo-assistant
4. confirmed Mixtral is default
5. confirmed also-available Claude 3-family and Llama 3 8b models, below
6. loaded https://people.com/angelina-jolie-and-brad-pitt-s-daughter-shiloh-18-files-to-drop-pitt-from-surname-8656440
7. clicked on Summarize this page
8. clicked on I understand
9. waited for output

Confirmed Mixtral summarized the page content

example	example

Upgrades - PASSED

Case 1: Non-Premium user (Claude 3 Haiku) - PASSED

Steps:

1. installed 1.66.118
2. launched Brave using --enable-features=AIChat:conversation_api\true --env-leo=staging --env-ai-chat.bsg=dev --env-ai-chat-premium.bsg=dev
3. opened brave://settings/leo-assistant
4. changed Default model for new conversations from Mixtral to Claude Instant
5. loaded https://en.wikipedia.org/wiki/Mozilla_Thunderbird
6. clicked on Show Sidebar
7. clicked on Leo
8. clicked on Summarize this page
9. NOTE: experienced a variant of Google doc summary is not rendered with Mixtral model when not opted in yet brave-browser#36086 😭
10. quit Brave
11. upgraded to 1.68.64, keeping profile intact, and renaming to Brave-Browser-Nightly
12. launched Brave
13. opened brave://settings/leo-assistant
14. confirmed Claude 3 Haiku is now shown as Default model for new conversations
15. clicked Summarize this page

Confirmed Claude 3 Haiku successfully summarized the Wikipedia page and supplanted Claude Instant, which is removed

example	example	example	example

Case 2: Premium user (Claude 3 Sonnet) - PASSED

Steps:

1. installed 1.66.118
2. launched Brave using --enable-features=AIChat:conversation_api\true --env-leo=staging --env-ai-chat.bsg=dev --env-ai-chat-premium.bsg=dev
3. purchased and loaded Leo Premium credentials from account.bravesoftware.com using [email protected]
4. set Default model for new conversations to Claude Instant in brave://settings/leo-assistant
5. loaded https://www.reuters.com/world/us/white-house-race-plunges-into-uncharted-territory-trump-awaits-july-sentencing-2024-05-31/
6. clicked on Summarize this page
7. clicked I understand
8. NOTE: experienced a variant of Google doc summary is not rendered with Mixtral model when not opted in yet brave-browser#36086 😭
9. quit Brave
10. renamed Brave-Browser profile to Brave-Browser-Nightly
11. installed 1.68.64
12. launched Brave using --enable-logging=stderr --v=2 --enable-features=AIChat:conversation_api\true --env-leo=staging --env-ai-chat.bsg=dev --env-ai-chat-premium.bsg=dev
13. opened brave://settings/leo-assistant
14. confirmed Claude Sonnet was the chosen default
15. returned to https://www.reuters.com/world/us/white-house-race-plunges-into-uncharted-territory-trump-awaits-july-sentencing-2024-05-31/
16. clicked on Summarize this page

Confirmed new default of Premium Claude 3 Sonnet replaced Claude Instant, and provided an accurate summarization

example	example	example	example	example