[EPIC] entrypoint.sh hardening audit (F2 round)

gh issue create --title "[EPIC] entrypoint.sh hardening audit (F2 round)" --label "epic,security,audit" --body "## EPIC: entrypoint.sh hardening audit (F2 round)

Source: F2 audit round, 2026-09-03. This EPIC aggregates the 9 findings from the entrypoint.sh audit (1 CRITICAL, 2 HIGH, 3 MEDIUM, 3 LOW).

The CRITICAL is a lock-release window during early-exit; should land in v2.11.3 alongside the lib.sh CRIT-1 (they are in the same RCE/credential-leak class). HIGH-2 is an unbounded-runtime bug; HIGH-1 is a retry-classification gap that complements #138.

### CRITICAL

- [ ] #188 entrypoint.sh C1 — EXIT trap releases concurrency lock BEFORE acquire returns (window 222->261)

### HIGH

- [ ] #138 TLS/handshake errors not classified as permanent (existing; F2 added detail; continuation of #138)
- [ ] #189 entrypoint.sh H2 — INPUT_MAX_RETRIES=0 + 5h timeout per attempt = unbounded total runtime

### MEDIUM

- [ ] #190 entrypoint.sh M1 — INPUT_SERVER not validated with validate_path; raw value flows into lftp -e
- [ ] #191 entrypoint.sh M2 — GITHUB_OUTPUT write aborts the rest of the script
- [ ] #192 entrypoint.sh M3 — /home/lftp/.lftp-logs grows unbounded across runs

### LOW

- [ ] #193 entrypoint.sh L1 — lftp log file is truncated on each retry; should append
- [ ] #194 entrypoint.sh L2 — print_resolved_config is not gated by INPUT_DEBUG
- [ ] #195 entrypoint.sh L3 — INPUT_SERVER with user:pw@ embedded makes lftp ignore .netrc

## Suggested resolution order

1. Land C1 in v2.11.3 with the lib.sh CRIT-1 (same credential-exfil class).
2. Land H2 + the permanent-error classifier (F2 detail on #138) together in v2.11.3.
3. Batch MEDIUMs into v2.11.4.
4. LOWs into a later cleanup release.

## Source

F2 audit 2026-09-03 (entrypoint.sh audit). Reporter: subagent-pekodbj7."