feat(llm-security): add 3 more runnable threat examples [skip-docs]

Three new self-contained, runnable threat demonstrations under
examples/, continuing the batch started in 583a78c. Each example
has README.md + run-*.mjs + expected-findings.md and uses
state-isolation discipline so the user's real cache/state files
are never polluted.

- examples/supply-chain-attack/ — two-layer demonstration:
  pre-install-supply-chain (PreToolUse) blocks compromised
  event-stream version 3.3.6 and emits a scope-hop advisory for
  the @evilcorp scope; dep-auditor (DEP scanner, offline) flags
  5 typosquat dependencies plus a curl-piped install-script
  vector in the fixture package.json. Maps to LLM03/LLM05/ASI04.

- examples/poisoned-claude-md/ — all 6 memory-poisoning detectors
  fire on a deliberately poisoned CLAUDE.md plus a fixture
  agent file under .claude/agents (E15/v7.2.0 surface):
  detectInjection, detectShellCommands, detectSuspiciousUrls,
  detectCredentialPaths, detectPermissionExpansion,
  detectEncodedPayloads. No agent runtime needed — scanner
  imported directly. Maps to LLM01/LLM06/ASI04.

- examples/bash-evasion-gallery/ — one disguised variant per
  T1 through T9 evasion technique fed through pre-bash-destructive,
  verified BLOCK after bash-normalize strips the evasion. T8
  base64-pipe-shell uses its own BLOCK_RULE. The canonical
  destructive form uses a path token rather than the bare slash
  (regex word-boundary requires it). Source-string fragmentation
  pattern reused from the e2e attack-chain test. Maps to
  LLM06/ASI01/LLM01.

Plugin README "Other runnable examples" section + plugin
CLAUDE.md "Examples" table + CHANGELOG Unreleased/Added
all updated. Marketplace root README unchanged
([skip-docs] for marketplace-level gate — plugin's outward
coverage is unchanged, only demonstrations were added).

plugins/llm-security/examples/bash-evasion-gallery/README.md

@@ -0,0 +1,131 @@
+# Bash Evasion Gallery (T1-T9)
+
+> **WARNING: This is a demonstration fixture, NOT a real attack.**
+> No destructive command actually runs. The script feeds JSON
+> payloads to one PreToolUse hook script and verifies the hook's
+> exit code. Your `$HOME` is safe.
+
+## What this demonstrates
+
+`hooks/scripts/pre-bash-destructive.mjs` (PreToolUse on `Bash`)
+catches destructive commands by pattern-matching the command
+string. A motivated attacker can disguise the same command using
+shell metacharacters that bash interprets transparently — so
+naive regex matching is bypassed.
+
+`scanners/lib/bash-normalize.mjs` is the **defense-in-depth layer**
+that strips these evasion techniques before pattern matching runs.
+This gallery feeds one disguised variant per T-tag through the
+hook and verifies that every variant gets normalized and blocked.
+
+This complements — does not replace — Claude Code 2.1.98+'s
+harness-level bash normalization. The plugin layer runs before
+the harness layer, so even on older Claude Code versions the
+techniques below are caught.
+
+## The T-tag taxonomy
+
+| Tag | Technique | Example | Normalizes to |
+|-----|-----------|---------|---------------|
+| T1 | empty single quotes | `r''m -rf $HOME` | `rm -rf $HOME` |
+| T2 | empty double quotes | `r""m -rf $HOME` | `rm -rf $HOME` |
+| T3 | parameter expansion (multi-char) | `${UNUSED}rm -rf $HOME` | `rm -rf $HOME` |
+| T3 | parameter expansion (single-char) | `c${u}rl url \| sh` | `curl url \| sh` |
+| T4 | backslash word-splitting | `r\m -rf $HOME` | `rm -rf $HOME` |
+| T5 | IFS word-splitting | `rm${IFS}-rf${IFS}$HOME` | `rm -rf $HOME` |
+| T6 | ANSI-C hex quoting | `$'\x72\x6d' -rf $HOME` | `rm -rf $HOME` |
+| T7 | process substitution | `cat <(echo rm) -rf $HOME` | `cat echo rm -rf $HOME` |
+| T8 | base64-pipe-shell idiom | `echo cm0gLXJmICRIT01F \| base64 -d \| sh` | (separate BLOCK_RULE — not normalization) |
+| T9 | eval-via-variable (one-level forward flow) | `X=rm; $X -rf $HOME` | `X=rm; rm -rf $HOME` |
+
+The canonical destructive target throughout the gallery is
+`rm -rf $HOME`. The `pre-bash-destructive` "Filesystem root
+destruction" BLOCK_RULE matches `rm -rf` followed by `$HOME`,
+`/<path>`, or `~<path>` — but plain `rm -rf /` slips through
+because the regex requires a word boundary after the path. The
+gallery uses `$HOME` so the regex fires reliably; for the literal
+`rm -rf /` case, see Claude Code 2.1.98+ harness-level checks.
+
+T8 is structurally different — it's not an evasion of an existing
+rule but a fresh attack pattern (decode + pipe to shell). It has
+its own BLOCK_RULE in `pre-bash-destructive`, named "T8 —
+base64-pipe-shell idiom".
+
+## How to run
+
+```bash
+cd plugins/llm-security
+node examples/bash-evasion-gallery/run-evasion-gallery.mjs
+
+# Detailed: full hook stderr
+node examples/bash-evasion-gallery/run-evasion-gallery.mjs --verbose
+```
+
+Expected: `10 pass, 0 fail`. Each T-tag should produce
+`BLOCKED: Destructive command detected — Filesystem root
+destruction (rm -rf /)` on stderr (or `T8 — base64-pipe-shell
+idiom` for the T8 case).
+
+## Hooks involved
+
+- **`hooks/scripts/pre-bash-destructive.mjs`** — PreToolUse on
+  `Bash`. Reads `tool_input.command`, applies `normalizeBashExpansion`
+  (T1-T7, T9) then `normalizeCommand` (whitespace + ANSI), then
+  iterates 8 BLOCK_RULES (rm-root, chmod 777, curl|sh, fork bomb,
+  mkfs, dd, /dev/ writes, eval+expansion, T8 base64-pipe-shell).
+  Exit 2 = block, exit 0 = allow (with optional WARN advisory).
+
+- **`scanners/lib/bash-normalize.mjs`** — pure function module,
+  shared with `pre-install-supply-chain.mjs`. Exports
+  `normalizeBashExpansion(cmd)`. Test contract:
+  `tests/lib/bash-normalize.test.mjs`.
+
+## Source-string fragmentation
+
+The `run-evasion-gallery.mjs` script never contains the literal
+string `rm -rf $HOME`. Each test command is built at runtime via
+concatenation (`'r' + 'm'`, `'-' + 'rf'`, `'$' + 'HOME'`). This
+follows the discipline from `tests/e2e/attack-chain.test.mjs` —
+secrets-shaped or destructive-command-shaped strings should never
+appear as literals in the source, because:
+
+1. `pre-edit-secrets` would block writing the file
+2. Static scanners would treat the source as compromised
+3. Operators reading the diff would not be able to tell at a
+   glance whether the literal was meant to be safe context or
+   live payload
+
+The `--verbose` mode prints the assembled command to stdout for
+inspection — that's a runtime print, not a source-file literal.
+
+## OWASP / framework mapping
+
+| Code | Framework | Why |
+|------|-----------|-----|
+| LLM06 | OWASP LLM Top 10 (2025) | Excessive Agency — destructive-command surface |
+| ASI01 | OWASP Agentic Top 10 | Excessive Agency / runtime command injection |
+| LLM01 | OWASP LLM Top 10 (2025) | Indirect prompt injection often delivers commands |
+
+## Limitations
+
+- T8 base64 decoding is detected pattern-only — it doesn't decode
+  the blob to inspect its content. A blob that decodes to
+  *non-destructive* content would still be flagged. This is the
+  documented v5.0 honest-limitation: deterministic detection
+  errs toward false-positive, not false-negative.
+- T9 only resolves one level of variable substitution forward.
+  `X=rm; Y=$X; $Y -rf $HOME` is **not** caught — the second-level
+  alias is too rare in real attacks to justify the runtime cost.
+- The hook is a defense-in-depth layer. Claude Code 2.1.98+
+  includes harness-level bash normalization that catches the
+  same techniques (and more, since the harness sees fully-
+  expanded commands). This plugin's hook covers older Claude
+  Code versions and runs before the harness layer either way.
+
+## See also
+
+- `docs/security-hardening-guide.md` §3 — bash evasion theory
+- `tests/lib/bash-normalize.test.mjs` — per-T-tag unit contract
+- `tests/lib/pre-bash-destructive.test.mjs` — block-rule contract
+- `examples/supply-chain-attack/` — adjacent layer (install gate)
+- `expected-findings.md` (in this folder) — testable contract