fix(events): cap stdin in the generated dispatcher, not just the CLI command

[Noor-ul-ain001]

Summary

• The fix: cap stdin read at 1 MiB to prevent DoS #3857 fix capped stdin at 1 MiB in specify event run (src/specify_cli/commands/event.py), but that CLI command is not the code path native hooks actually invoke.
• Every installed integration writes a self-contained .specify/events.py dispatcher (the _EVENTS_DISPATCHER_TEMPLATE string in src/specify_cli/events.py), and native hook configs call that dispatcher directly. Its main() did:

  payload = sys.stdin.read() if not sys.stdin.isatty() else "{}"

  with no size cap at all — the exact DoS fix: cap stdin read at 1 MiB to prevent DoS #3857 was meant to close, wide open on the primary invocation path. specify event run is a secondary/manual entry point; the generated dispatcher is what actually runs on every session_start/pre_tool_use/etc. hook fire in real usage.
• Fix: apply the same byte-capped read (from the binary buffer, so the cap counts encoded bytes rather than decoded characters) inside the dispatcher template, so every newly-installed or refreshed dispatcher enforces the limit.

Test plan

• Added 3 tests in tests/integrations/test_events.py::TestCommandRunner: an oversized payload exits 1 with the limit message instead of running unbounded, a multibyte payload (~300k emoji, ~1.14 MiB UTF-8 but only 300k characters) is still rejected by the byte-based cap, and a normal under-the-cap payload still reaches the handler script unchanged.
• Verified both new tests fail without the fix (test-the-test): the oversized-payload test failed because the dispatcher silently accepted the full payload and returned "not found" instead of exiting 1 with the limit message — reproducing the exact bug.
• Ran the full tests/integrations/test_events.py suite: 124/128 pass; the remaining 4 are pre-existing Windows symlink-elevation failures unrelated to this change.

Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com

https://claude.ai/code/session_01PJHJ2dHP2RVCNncHqN8Qm9