chore: update to our fork of charm.land/fantasy with appendCompact perf improvement

[johnstcn]

Fixes CODAGT-117

Updates go.mod to reference our forks of the following dependencies:

• charmbracelet/anthropic-sdk-go => https://github.com/coder/anthropic-sdk-go/tree/coder_2_33
• charm.land/fantasy => https://github.com/coder/fantasy/tree/coder_2_33

[Copilot]

Pull request overview

Updates Go module dependencies to newer internal fork revisions to pick up performance improvements (notably appendCompact) and align the Anthropic SDK fork with the coder_2_33 tracking described in the PR.

Changes:

• Bump charm.land/fantasy replacement to a newer github.com/coder/fantasy pseudo-version (perf improvement referenced in comments).
• Switch github.com/charmbracelet/anthropic-sdk-go replacement from github.com/kylecarbs/anthropic-sdk-go to github.com/coder/anthropic-sdk-go at a newer pseudo-version.
• Drop github.com/charmbracelet/openai-go from go.mod indirect requirements and remove corresponding go.sum entries.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 2 comments.

File	Description
go.mod	Updates replace directives for fantasy and Anthropic SDK forks; removes unused indirect charmbracelet/openai-go requirement; adds clarifying comments.
go.sum	Refreshes module checksums to match updated fork pseudo-versions and removed dependency entries.

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[johnstcn]

review: moved these up to keep them with the other perf improvements

[johnstcn]

Smoke-tested both OpenAI and Anthropioc agents with develop.sh

[johnstcn]

@ibetitsmike does this need a cherry?

[ibetitsmike]

@johnstcn the token accounting thing is important, but neglibale for EA