feat: configurable history limits (improved)

[roman0yurin]

Issue for this PR

No linked issue for this revised PR.

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

This PR is a revised version of the history limits feature work. It makes the history/compaction limits configurable at runtime instead of relying only on hardcoded defaults.

Changes included:

• Extend the server config schema with compaction limit settings and validation bounds.
• Apply the configured compaction limits in runtime compaction logic.
• Update the configuration documentation to describe the new fields and defaults.
• Update generated SDK types so clients can use the new config fields.

Why this works:

The new limits are now read from the validated server config and used by compaction at runtime, with safe fallbacks to the existing defaults when the config is not set.

Files touched:

• packages/opencode/src/config/config.ts
• packages/opencode/src/session/compaction.ts
• packages/opencode/src/session/prompt.ts
• packages/opencode/src/session/processor.ts
• packages/web/src/content/docs/config.mdx
• packages/sdk/js/src/v2/gen/types.gen.ts

How did you verify your code works?

• bun turbo typecheck
• bun test --cwd packages/opencode test/session/compaction.test.ts

Screenshots / recordings

N/A (no UI changes)

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR