feat: --auto option, unlock auto/bypassPermissions permission modes via canonical claude-* model names

[BenSheridanEdwards]

Claude Code disables auto and bypassPermissions modes when ANTHROPIC_DEFAULT_*_MODEL is not a claude-* value. Today deepclaude exports the resolved backend model names (e.g. deepseek-v4-pro) directly, which trips that gate — Shift+Tab reports "auto mode isn't available for this model".

This PR adds a --auto opt-in that swaps the env vars to canonical claude-* names so the gate unlocks. Default behavior is unchanged: backend-native names in env vars and TUI, no auto/bypassPermissions. The bulk of the diff is proxy hardening that's needed regardless of which mode you launch in.

Behavior

deepclaude (default, no --auto):

• Proxy starts; request flows claude → proxy → deepseek (or or/fw).
• Env vars set to backend names (deepseek-v4-pro, deepseek-v4-flash, etc.).
• TUI shows the real backend model.
• Shift+Tab cannot reach auto / bypassPermissions.
• Launch banner prints:

  Auto mode: OFF (running deepseek; TUI will show 'deepseek-v4-pro')
  Tip: pass --auto to enable auto mode — TUI will show 'claude-opus-4-7' instead
  

deepclaude --auto:

• Same proxy path; env vars switched to canonical claude-opus-4-7 / claude-sonnet-4-6 / claude-haiku-4-5-20251001.
• Proxy MODEL_REMAP translates them back to backend names on the wire (#N model remap: claude-opus-4-7 → deepseek-v4-pro in $PROXY_LOG).
• TUI shows claude-opus-4-7 (it lies — actual routing is still the configured backend).
• Shift+Tab cycles default → auto → plan → bypassPermissions.

Caveat (auto mode only): Claude Code's in-session UI (status bar, /model) shows the canonical claude-* name rather than the backend model — the trade-off for unlocking auto-mode. The launch banner still prints the resolved backend name, and the proxy logs every remap, so the actual routing is verifiable from outside the TUI.

What's in the diff

Behavior gate:

• New --auto flag (default off). set_model_env branches on it: auto = canonical claude-* names, default = $RESOLVED_OPUS / $RESOLVED_SONNET / $RESOLVED_HAIKU / $RESOLVED_SUBAGENT.
• New print_auto_mode_tip helper called by both launch_claude and launch_remote so the trade-off is visible at launch in either mode.
• --help documents --auto.

Proxy / launch hardening (active in both modes):

• Route the default launch_claude path through the local proxy (mirrors what launch_remote already did), so requests go through the same code path regardless of mode.
• start-proxy.js legacy mode accepts an optional 3rd-positional defaultMode, so state.mode resolves to deepseek / openrouter / fireworks (not _single or anthropic) and MODEL_REMAP[state.mode] actually fires. This also fixes a latent bug in launch_remote, which previously left the proxy in 'anthropic' mode and forwarded requests to api.anthropic.com regardless of the configured backend.
• Add Fireworks entry to MODEL_REMAP to match deepseek/openrouter.
• Extract a shared start_proxy helper used by both launch_claude and launch_remote. Symlink-resolve SCRIPT_DIR so deepclaude works when installed via a /usr/local/bin/deepclaude symlink.
• Call start_proxy directly (not via $()) so the PROXY_PID it sets actually reaches the parent shell — the EXIT trap was previously a silent no-op, leaving the node proxy orphaned on exit. start_proxy now sets PROXY_PID, PROXY_PORT, and PROXY_LOG as script globals.
• Align RESOLVED_HAIKU / RESOLVED_SONNET / RESOLVED_SUBAGENT with what MODEL_REMAP actually produces, so the launch banner matches the wire instead of advertising the pro model for slots the proxy routes to flash.
• Use a per-instance $PROXY_LOG path (/tmp/deepclaude-proxy.$$.log) so concurrent invocations don't truncate each other's logs. The resolved path is printed at launch.
• On a non-zero, non-signal claude exit, dump the tail of $PROXY_LOG to stderr so upstream proxy errors and remap warnings surface immediately. Clean exits and Ctrl+C stay silent.
• Warn in the proxy when a request arrives with a claude-* model name not in MODEL_REMAP[state.mode] — catches drift between the canonical-name list in deepclaude.sh and the remap table the next time Anthropic ships a model bump. Backend-native names (default-mode wire format) are passed silently.
• Document the start-proxy banner-ordering invariant that grep -E '^[0-9]+$' depends on, plus a sync-required note above set_model_env.

Notes for reviewers

• This overlaps with draft PR fix: route default launch through proxy (fixes cost tracking and auth override) #9 on the proxy-routing piece. PR fix: route default launch through proxy (fixes cost tracking and auth override) #9 fixes cost-tracking but does not switch model env vars to canonical claude-* names, so PR fix: route default launch through proxy (fixes cost tracking and auth override) #9 alone does not unlock auto mode.
• This branch deliberately does NOT alter the existing thinking-strip policy from 70518b6. A separate experiment branch tests scoping that strip down for DeepSeek; results will inform a follow-up.
• Manual verification: confirmed Shift+Tab cycles modes locally with backend ds under --auto, and that default mode shows backend names in the TUI with the expected tip in the launch banner. Static review only for or and fw paths — keys not present in test environment.