feat(agent): unify tool failure status contract and remove null-status error paths (T38)

[konlue]

Describe what this PR does / why we need it

Part 1 of T38 (#141), following the "keep it simple" agreement: unify the tool failure status contract so error exits produce a machine-readable status instead of a status-less response, and define the canonical outcome vocabulary.

Scope note (updated after merging main): the big model-SDK decoupling refactor (#152) landed mid-review and removed the ToolExecutionExceptionProcessor path in AgentToolNode — one of the three null-status pseudo-success exits this PR targeted — replacing it with the neutral ToolResult contract that already maps failures to the error status. This PR now covers the remaining ground:

• ToolOutcome: a constants class defining the canonical outcome vocabulary from the issue (success / error / validation-denied / auth-denied / business-failed / transient / timeout / cancelled / uncertain). SUCCESS and ERROR keep the existing string values; the reserved values are declared now and wired to their producers in the follow-up (PR2: business-failure mapping + model-visible consistency).
• ToolRetryInterceptor: the exhausted-retries exit returns an explicit error response instead of of(...).
• ToolErrorInterceptor: the swallowed-handler-exception exit likewise returns an explicit error response.
• ToolCallResponse.of() javadoc now documents its status-less historical shape and points new code at the status-carrying factories. The ERROR_STATUS constant (introduced on main by refactor: decouple ARGI runtime from model SDKs #152 and independently by this branch) is kept as a single declaration.

Does this pull request fix one issue?

NONE

Describe how you did it

• New ToolOutcome constants class next to ToolCallResponse; the status field stays a String (claim-question 1: starting with the low-invasive option).
• ToolRetryInterceptor / ToolErrorInterceptor now return ToolCallResponse.error(...) on their failure exits, so those responses carry status = "error" plus the standard error/errorMessage metadata.
• Merged with main's refactor: decouple ARGI runtime from model SDKs #152 refactor (merge commit included): the removed processor path and its test were adapted to the neutral API; an async symmetric test keeps the sync/async consistency acceptance criterion covered.

Describe how to verify it

• AgentToolNodeFailureMetadataTest: sync and async wrapped-exception paths both assert status == "error" / isError() == true with the wrapped exception type in metadata (the async case is new here).

• ToolRetryInterceptorUnitTest: exhausted-retry response asserts the error status and error/errorMessage metadata.

• New ToolErrorInterceptorTest (2 cases) covering pass-through and the explicit error shape.

• Run:

  ./mvnw -pl argi-agent-framework -am test -DskipTests=false \
    -Dtest='AgentToolNodeFailureMetadataTest,ToolRetryInterceptorUnitTest,ToolErrorInterceptorTest,ToolCallResponseTest' \
    -Dsurefire.failIfNoSpecifiedTests=false

Special notes for reviews

• Behavior change: responses on the two fixed exits now have status = "error" (previously null), so isError() flips from false to true there. The retry interceptors only compare against SUCCESS_STATUS — a null status already counted as non-success — so retry behavior is unchanged.
• The exhausted-retry and swallowed-error responses now carry an Error: result prefix plus error/errorMessage metadata (the formatted message is still in the result).
• Full regression after merging main shows only pre-existing Windows failures (the 5 skills/prompt-template cases reproduce identically on clean main ee72a721c, as do the 3 FileSystemStoreTest drive-root errors).
• Question 2 from the claim comment (model-visible outcome in ToolResponseMessage metadata) stays with the follow-up PR together with the business-outcome mapper.

[yuluo-yx]

hi @konlue 合并了一个比较大的 pr，有些冲突，可以解决下 🌹

[konlue]

hi @konlue 合并了一个比较大的 pr，有些冲突，可以解决下 🌹

@yuluo-yx 已解决 🌹

merge 了 main（#152 重构 + #157/#158），冲突在 ToolCallResponse / AgentToolNode / 失败元数据测试三处：#152 移除的 ToolExecutionExceptionProcessor 路径（正是本 PR 要修的 null-status 出口之一）以重构的新结构为准，我的状态契约改动收敛到剩余两个出口（重试耗尽 / 异常吞掉）+ ToolOutcome 词汇表，另补了 async 对称测试。

PR 描述已同步更新。