Expose stable structured error codes

[cervantesh]

Summary

• export stable SmartEditErrorCode and SmartEditError contracts with redacted structured details
• centralize normalization for core [E_*] returns/throws, policy, filesystem, CLI/schema, and Pi mutation queue failures
• preserve readable diagnostics and the existing single stale-anchor retry while making library failures reject and CLI failures deterministic
• document the public taxonomy, redaction decision, and compatibility migration from resolved error strings
• add cross-surface parity and failure nonmutation coverage

Validation

• npm ci --ignore-scripts
• npm run check
• npm run build
• npm test (38 passed, 1 capability-based Windows permission skip)
• npm run coverage (98.44% lines, 100% functions, 90.91% branches)
• npm run benchmark (5.92 ms / 20,000 operations; 1000 ms budget)
• npm run verify:dependencies
• npm run verify:policy
• npm run verify:workflows
• npm run verify:release (27 package files)
• npm pack --dry-run
• npm audit --omit=dev --audit-level=high
• npm audit --audit-level=high
• git diff --check

Closes #32

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reject stale errors without parseable suggestions

When a PiClient throws the new structured SmartEditError with code === E_STALE_ANCHOR but a message that is not the legacy [E_STALE_ANCHOR] stale-suggestion payload, this catch path assigns the human message to first; parseStaleAnchorError(first) then reports stale: false, so replaceAnchoredWithRetry returns the error text as a successful edit result. This can silently swallow failures for custom adapters using the public structured error contract; if the stale payload cannot be parsed, the session should reject rather than treat it as success.

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