fix(tui-gateway): restore token counters on session.resume for correct Desktop usage display

[liuhao1024]

Problem

When viewing a gateway session (e.g. Telegram) in Hermes Desktop, the bottom status bar always shows 0/1.0M-0% for context usage. Token usage information is missing even though the session duration is recorded correctly.

Root Cause

session.resume in the TUI gateway builds a fresh AIAgent whose token counters (session_input_tokens, session_output_tokens, etc.) all start at zero. The actual cumulative usage is stored in state.db (written by update_token_counts() on every API call), but it was never loaded back into the agent.

When _session_info(agent, session) calls _get_usage(agent), it reads the zero-initialized counters, so session.info and session.usage both report all-zero usage back to Desktop.

Fix

Add _restore_session_usage(agent, stored) — called after _make_agent() in the session.resume handler — that copies the stored token counts from the DB session row into the agent's runtime counters:

• input_tokens → agent.session_input_tokens
• output_tokens → agent.session_output_tokens
• cache_read_tokens → agent.session_cache_read_tokens
• cache_write_tokens → agent.session_cache_write_tokens
• reasoning_tokens → agent.session_reasoning_tokens
• api_call_count → agent.session_api_calls
• estimated_cost_usd → agent.session_estimated_cost_usd
• cost_status → agent.session_cost_status

session_total_tokens is computed as the sum of the five token components.

Files Changed

• tui_gateway/server.py — _restore_session_usage() helper + call in session.resume
• tests/tui_gateway/test_restore_session_usage.py — 7 tests (unit + _get_usage integration)

Testing

tests/tui_gateway/test_restore_session_usage.py — 7 passed

Closes #42989

[teknium1]

Thanks for tracing the durable token counters and adding focused helper coverage.

Problems

• The restore call added by this PR is only in the eager resume branch. Current Desktop intentionally calls session.resume without eager_build (apps/desktop/src/app/session/hooks/use-session-actions/index.ts:503-510), so current main takes the deferred path (tui_gateway/server.py:5721-5767). Its later _start_agent_build creates the agent at tui_gateway/server.py:1382 and emits session.info at :1445 without restoring the stored usage. The Desktop path in the report therefore remains unfixed.

Suggested changes

• Preserve the loaded session row in the deferred record and restore its counters immediately after _make_agent() in _start_agent_build; retain equivalent eager-path coverage.
• Add a non-eager_build Desktop-resume integration test that verifies the deferred session.info usage payload.

Automated hermes-sweeper review.

[teknium1]

Desktop no longer takes this eager branch: it omits eager_build in apps/desktop/src/app/session/hooks/use-session-actions/index.ts:503-510, so current main defers through tui_gateway/server.py:5721-5767. _start_agent_build then creates the agent and emits session.info without a restore (tui_gateway/server.py:1382,1445). Carry the stored row into that deferred record and restore there too.