fix(agent-os): detect context-cued bare SSNs in redactor and adapter PII patterns

[dylanyunlon]

Closes #3592

Problem

CredentialRedactor.PII_PATTERNS and integrations.base.PII_PATTERNS both require a separator between digit groups so that bare nine-digit numbers (tracking numbers, ZIP+4, ABA routing numbers) do not hard-block at the MCP gateway. That requirement also lets a genuine SSN through when it is written without separators next to an explicit cue:

• SSN: 745102386
• ssn=745102386
• social security number 745102386

None of these match at either detector today (verified against both patterns), so tool output carrying a cued bare SSN is neither redacted at the gateway nor blocked by the adapters.

Fix

Add a "US SSN (context-cued)" pattern to both detection sites. The pattern fires only when a case-insensitive cue keyword (ssn, social security, social security number/num/no/#, soc sec) appears immediately before the nine-digit run, keeping uncued bare digits as non-matches so the false-positive suppression from #3531 is preserved. Both detectors carry the identical regex to stay in lockstep (#3591 tracks their alignment).

Call chain (2 entry points, 2 source files, 2 test files)

Entry point	Guard
CredentialRedactor.find_pii_matches()	PII_PATTERNS["US SSN (context-cued)"].pattern
adapter PII scan (autogen/bedrock)	integrations.base.PII_PATTERNS[1]

Files changed (5)

File	Change
agent-governance-python/agent-os/src/agent_os/credential_redactor.py	New US SSN (context-cued) CredentialPattern with cue-anchored regex
agent-governance-python/agent-os/src/agent_os/integrations/base.py	Mirrored context-cued regex in PII_PATTERNS tuple (index 1)
agent-governance-python/agent-os/tests/test_credential_redactor.py	18 new tests (11 positive cued matches, 6 negative uncued stability, 1 matched_text assertion)
agent-governance-python/agent-os/tests/test_pii_patterns.py	9 new tests (5 positive cued matches, 4 negative uncued stability)
CHANGELOG.md	### Fixed entry under [Unreleased]

Tests

18 new tests over the two detection call chains:

• test_context_cued_bare_ssn_is_detected (11 tests): every cue variant from the issue (SSN:, ssn=, social security number, Social Security, soc sec, socsec, etc.) with a bare nine-digit run.
• test_context_cued_ssn_does_not_match_uncued_bare_digits (6 tests): uncued bare digits (tracking numbers, invoices, routing numbers, phone-like) are NOT matched — preserves fix(agent-os): detect separated SSN forms without matching bare nine digits #3531 FP suppression.
• test_context_cued_ssn_match_captures_digits_only (1 test): the matched_text includes the digit run for redaction.
• test_shared_context_cued_ssn_matches_cued_bare_digits (5 tests): adapter-side PII_PATTERNS[1] matches cued forms.
• test_shared_context_cued_ssn_rejects_uncued_bare_digits (4 tests): adapter-side pattern rejects uncued forms.

All 125 existing + new tests pass.

Signed-off-by: dylanyunlon dogechat@163.com

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PR Review Summary

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[MohammadHaroonAbuomar]

• CI 'Spell-check changed files' fails on this PR's own added lines: Spell-check changed files (unknown words in added lines: uncued, undelimited, socsec, ISSN, Confessn); Please add the terms to .cspell-repo-terms.txt (or reword) so the gate passes.

[dylanyunlon]

Right, should have caught the spell-check gate before pushing. Confirmed all five words are flagged on the added lines: uncued, undelimited, socsec, ISSN, Confessn.

Fixed in 03cfdd2:

• Added all five terms to .cspell-repo-terms.txt in alphabetical position. socsec is a cue keyword in the regex alternation, uncued/undelimited appear in test names and comments, and ISSN/Confessn are the negative test cases from the boundary fix in bbcf358.
• No code change, dictionary only.

131 tests pass.

[MohammadHaroonAbuomar]

• The PR no longer merges: GitHub reports CONFLICTING and a local git merge origin/main conflicts in agent-governance-python/agent-os/src/agent_os/integrations/base.py (PII_PATTERNS, lines 22-36 of the merged file). Main (#3532 fix) replaced the first SSN regex with re.compile(r"(?<![A-Za-z0-9])\d{3}[\s.-]\d{2}[\s.-]\d{4}(?![A-Za-z0-9])") plus a long comment; this branch keeps the old \b\d{3}[\s.-]?\d{2}[\s.-]?\d{4}\b line and inserts the cued pattern after it. Rebase onto current main (branch is 161 commits behind) and resolve by keeping main's separator-required line and comment, then the new context-cued re.compile(...) block directly after it, before the email regex. Verified: with exactly that resolution tests/test_credential_redactor.py and tests/test_pii_patterns.py pass on main (155 passed). The rebase also picks up main's typing-extensions==4.16.0 pin in agent-governance-python/requirements/ci-test.txt, which fixes the cannot import name 'sentinel' from 'typing_extensions' collection errors that failed test (agent-os, 3.11/3.12/3.13) on the previous head bbcf358.