fix: let a folder turn explanation off, or on with its own provider

[shenxianpeng]

Description

A folder's settings did not decide whether its jobs are explained.

• A folder could not turn explanation off. The box at the top of the folder's section, Enable AI Error Explanation, only opens the section. Left unticked, which it is by default, the folder sets nothing and its jobs follow the global switch. Builds in a folder that looked switched off were still sent to the provider.
• A folder with a provider of its own had no Explain Error button while the global switch was off. The console page's endpoint refused with "disabled in global configuration", although explainError() and automatic explanation in the same folder used the folder's provider.

Now:

• The folder section has Turn off AI error explanation for jobs in this folder. With it there is no button, no automatic explanation, and explainError() does nothing. Explanations builds already have can still be read.
• The box that opens the section is renamed Set AI error explanation for this folder, which is what it does.
• The nearest folder that decides wins: one that turns explanation off says no, one with a provider of its own says yes. Otherwise the global switch applies.
• The console and Stages pages and their endpoints ask that question for the build in front of them. A folder with its own provider gets the button while the global switch is off, and the provider named on the button is the folder's.

Before and after

The folder's section

Before	After
Unticked by default, so the folder looks switched off. It is not.	The box says what it does, and turning explanation off is its own setting.

A failed build in that folder, global switch on

Before	After
The button is there and the log goes to the global provider.	No button. The endpoint answers "AI error explanation is turned off for this job.", and automatic explanation skips the build.

A failed build in a folder with its own provider, global switch off

Before	After
No button, while explainError() in the same folder works.	The button is there, and the explanation comes from the folder's provider (its model, mobile-team-model, is in the footer).

The screenshots use a local stand-in provider with canned answers.

Things a reviewer should know

• No folder changes behaviour on upgrade. enableExplanation keeps its stored meaning: "the section is in use". Every folder whose Configure page was saved before 216 has it stored as false, so giving that value the meaning "off" would have switched those folders off. Turning off is a new field, disableExplanation.
• A subfolder can turn explanation on again below a folder that turned it off, by setting a provider of its own. This follows the rule the plugin already had: a folder provider wins over the global switch being off. If an off folder should be final for everything below it, that is a small change in ExplainErrorFolderProperty.findFolderDecision.
• One edge case changes. A folder whose section is unused but that has a provider stored, which an older form did by accident (fix: stop the folder form from saving a provider nobody chose #243), used to stop the provider lookup, so its jobs got the global provider even under a parent folder with its own. The lookup now passes over it, as the enabled check already did, and the parent's provider applies.
• The console endpoint's refusal now reads "AI error explanation is turned off for this job." instead of "AI error explanation is disabled in global configuration.", since it may come from a folder.
• The global setting keeps its label, Enable AI Error Explanation; only the folder's box is renamed.
• ExplainErrorFolderProperty.isFolderExplanationEnabled is unused and kept as it was.

Related Issues

None; found while reviewing what to fix next.

Testing done

• FolderExplanationSwitchTest, 10 new tests: a folder turning explanation off while it is on globally (explainer, console page and endpoint, explainError(), automatic explanation); a folder with its own provider while it is off globally (console page and endpoint, Graph View endpoint); the nearest folder deciding in both directions; folders stored before keeping the global switch; an unused section passing the parent's provider on; the switch saved through the folder form.
• Existing test classes pass: ExplainErrorFolderPropertyTest, ErrorExplainerTest, ConsolePageDecoratorTest, ConsoleExplainErrorActionTest, GraphViewExplainErrorActionTest, PipelineGraphViewDecoratorTest, AutoExplainJobOverrideTest, AutoExplainLimitsTest, ErrorRunListenerTest, ExplainCardStatesTest, ConsoleToolbarTest, CasCTest, ConfigMigrationTest, ExplainErrorStepTest, ExplanationReuseTest, UsageTrackingTest, QuotaEnforcerTest.
• SpotBugs: no findings. The full mvn verify was not run locally.

By hand, on a local Jenkins 2.528.3 with a stand-in provider that counts its requests, the same folders before and after:

Checked	Before (main)	After
A folder meant to be off, global on: console of a failed build	Box left unticked, as off as the form allowed: button, explained by the global provider	Turned off on the form: no button; the endpoint refuses; 0 requests
Same folder, automatic explanation on	Not checked	Not explained, nothing in the build log, 0 requests
Same folder, a build explained before it was turned off	Not applicable	Explanation still shown, no re-explain control
Folder with its own provider, global off: console of a failed build	No button; the endpoint refuses	Button; explained by the folder's provider

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed

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Assisted-by: Claude Code (claude-opus-5-5)