feat(coding-agent): add auto approval classifier

[realsigridjin]

Summary

• add auto as a first-class permission preset for settings, --permission-preset, and the Alt+A session cycle
• classify every otherwise-pending tool proposal, including in-project edits, with a reasoning-blind two-stage model gate
• keep assistant reasoning and tool outputs out of classifier context; only user messages and the current proposal are visible
• preserve explicit settings/CLI rule precedence and escalate blocked, malformed, or unavailable classifier decisions to normal user approval
• keep Shift+Tab dedicated to thinking-level cycling and the manual workspace, read-only, and ask modes available

Design

The implementation follows the auto-mode classifier architecture described by Anthropic and evaluated in AmPermBench:

• fast stage: exact ALLOW or REVIEW
• review stage: concise reasoning ending in DECISION: ALLOW or DECISION: BLOCK
• fail closed: any block, malformed response, credential failure, timeout, or provider error falls back to user approval
• no tool-name or prompt-keyword allowlist; default auto decisions are model-based
• unlike the evaluated Tier 2 bypass, project file edits also pass through the classifier

References:

• https://arxiv.org/html/2604.04978v2
• https://www.anthropic.com/engineering/claude-code-auto-mode

Verification

• npm run check
• npm run build -w @code-yeongyu/senpi
• focused permission/shortcut suite: 254 passed
• real AgentSession + faux-provider tool-call path: classifier invoked, bash executed, assistant reasoning absent from classifier context
• broad suite excluding two unchanged unrelated flaky files: 6,772 passed, 35 skipped, 0 failed

The unfiltered full suite exposed two pre-existing failures outside this diff: a reftable refresh timeout and a 1 ms app-server archive timestamp comparison. The affected files are unchanged from origin/main.

[realsigridjin]

@code-yeongyu All CI checks are green. I do not have upstream merge permission; please merge this PR when ready.

[realsigridjin]

@code-yeongyu Updated and synchronized: Shift+Tab now remains the thinking shortcut, approval mode uses Alt+A, and the branch includes latest main without conflicts. All 14 checks pass on head f4fc7d9. I still lack upstream merge permission; please merge when ready.

[realsigridjin]

@code-yeongyu i need this feature