doctor: stop planning a TUI config entry on OpenCode 2

[coleleavitt]

Linked issue

Approved issue: #367

What changes

• HarnessAdapter gains an optional tuiPluginEntryApplies(). OpenCode answers configGeneration() !== "v2"; adapters that don't implement it keep today's behaviour.
• buildDoctorFixPlan skips the "(TUI sidebar)" item when it returns false, and the --fix apply loop skips calling ensureTuiPluginEntry for the same case, so the plan and the applied changes agree.
• hasTuiPluginEntry() is untouched, so diagnostics still report what the file contains.

How it was checked

• bun test in packages/aft-cli: 360 pass.
• New tests: the plan has no TUI item when the adapter says it doesn't apply, still has it when it applies or doesn't say (doctor.test.ts); OpenCodeAdapter.tuiPluginEntryApplies() is true for V1 and false for V2 (opencode-generation-config.test.ts). The V2 plan test fails without the doctor.ts change.
• tsc --noEmit and biome check packages/aft-cli/src clean.
• By hand: on OpenCode 2.0.18, doctor --fix previously listed "Will add … to tui.json (TUI sidebar)"; with this change that line is gone.

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Summary by cubic

Stops doctor from planning a TUI sidebar entry on OpenCode 2, where the plugin is loaded from the package's own entrypoint and no tui.json is read, so the plan no longer offers a repair that writes nothing (issue #367).

• HarnessAdapter gains an optional tuiPluginEntryApplies(); OpenCode returns configGeneration() !== "v2", and adapters that don't implement it keep today's behavior.
• buildDoctorFixPlan and the --fix apply loop skip the TUI entry when it returns false, so the plan and applied changes agree.
• hasTuiPluginEntry() is untouched, so diagnostics still report what the file contains.

^{Written for commit 5d4cd1a. Summary will update on new commits.}

[cortexkit-ci]

#367 has the design-approved label; this PR can be reviewed.

[aft-alfonso]

Merged, thanks @coleleavitt. doctor --fix on OpenCode 2 no longer lists a tui.json change. It ships in the next release, where the release notes credit you.