fix(normalizer): word-boundary check in classifyShellRisk — closes #63

[jpleva91]

Summary

• Replaces strings.HasPrefix(trimmed, prefix) with trimmed == cmd || strings.HasPrefix(trimmed, cmd+" ") in classifyShellRisk
• Closes the false read-only classification gap: commands like catalog_tool --delete, finder.sh --purge, or echo 'rm -rf /' | bash no longer match read-only prefixes cat, find, echo
• All legitimate matches preserved: bare commands and commands-with-arguments both work correctly

Root cause

strings.HasPrefix matches any string sharing a prefix byte-for-byte, regardless of word boundaries. A command named catalog_tool is not cat, but the old code classified it as RiskReadOnly because "catalog_tool" starts with "cat".

The most dangerous false positive: echo 'rm -rf /' | bash classified as read-only, reducing governance fidelity (though policy enforcement would still catch the rm in destructive scan).

Fix

// Before
if strings.HasPrefix(trimmed, prefix) {
    return action.RiskReadOnly
}

// After — exact match OR followed by space (word boundary)
if trimmed == cmd || strings.HasPrefix(trimmed, cmd+" ") {
    return action.RiskReadOnly
}

Test plan

• go build ./... passes
• Manual: verify catalog_tool --delete → RiskMutating (not RiskReadOnly)
• Manual: verify cat file.txt → RiskReadOnly (still correct)
• Manual: verify go test ./... → RiskReadOnly (space-separated multi-word command preserved)
• CI green

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