Shell serial stack: here-strings, heredoc terminators, arithmetic/comment openers, secret ordering

[TheGreatAxios]

Stacks four shell-serial fixes (0.3.24 posture: open only, do not merge).

Issues: CL-7319, CL-7386, CL-7387, CL-5420.

Commits (in order):

1. a4e5812 — Treat here-strings as inline arguments, never heredoc openers (CL-7319). Acceptance: cat <<< word parses the word as an inline argument; no heredoc body is opened and the following chain still splits.
2. 32e6d6e — Match heredoc terminators exactly, tab-stripping only for <<- (CL-7386). Acceptance: a space-indented marker does not close plain <<; CRLF markers compare CR-stripped; splitter and approval display agree on where the heredoc ends.
3. 4cebff2 — Ignore heredoc openers inside arithmetic and comments (CL-7387). Acceptance: << inside ((/$((is left-shift and after a top-level#is documentation, so neither opens a heredoc. Follow-up fix folded in: the comment guard is a commentToEOL flag that suppresses ONLY the<<branch — operators after#still split, sosplitChainedCommand("# note && rm -rf /")surfacesrm -rf /` as its own segment.
4. 50e0681 — Lock secret-before-listing ordering for shell secret paths (CL-5420). Acceptance: pure ls of a secret name still asks, chains flag the content-reading half, bounded listings stay exempt, unbounded listings still ask.

Verification:

• bun test src/permission/permission.test.ts src/tui/command-display.test.ts src/permission/command.test.ts src/permission/classify-security.test.ts tests/unit/permission/cross-commit-composition.test.ts → 426 pass, 0 fail
• bun run typecheck (tsc --noEmit) → clean
• bunx oxlint on touched files → clean
• bun run check → sole red is pre-existing oxfmt on untouched src/subagent/spawn-agent-worktree.test.ts (not in this branch diff; fails on main too)
• Display verbatim behavior unchanged (only newline splits there); 7319/7386/5420 hunks untouched.