chore!: bump coder/coder SDK and remove model cost settings

[ethanndickson]

Bumps github.com/coder/coder/v2 from the previously pinned main commit (fbac602456c9, 2026-07-28) to a newer main commit (fa8ffe4eda92, 2026-08-18).

Resulting module version: v2.34.0-rc.0.0.20260818054033-fa8ffe4eda92

Breaking change

This SDK bump removes pricing fields from coderd_agents_model.model_config. The following settings are no longer supported and must be removed:

model_config = jsonencode({
  cost = {
    input_price_per_million_tokens  = "3"
    output_price_per_million_tokens = "15"
  }
})

The four legacy top-level pricing settings are also removed:

• input_price_per_million_tokens
• output_price_per_million_tokens
• cache_read_price_per_million_tokens
• cache_write_price_per_million_tokens

The provider validates model_config against its pinned SDK. Configurations with these pricing settings will fail at plan time. Remove these settings before you upgrade the provider. Coder now gets cost data from AI Gateway.

The example and generated documentation remove model_config.cost.

Compatibility

This SDK bump does not set a new minimum Coder version for the coderd_template resource. The follow-up #414 adds the optional agents_allowed attribute. Explicit use of that attribute requires Coder v2.37.0 or later.

Release context

This change requires a provider release that is marked as breaking. The release notes must include the model_config pricing migration. The breaking change applies to coderd_agents_model.

This is the prerequisite layer for #414.

Refs https://linear.app/codercom/issue/CODAGT-716/expose-agents-allowed-in-the-coderd-terraform-provider

Stack plan

1. Update the Coder SDK and remove obsolete chat model cost configuration.
2. Add agents_allowed to the coderd_template resource and data source in feat(coderd_template): expose agents_allowed #414.

Opened by Coder Agents on behalf of @ethanndickson.

[linear-code]

CODAGT-716