fix(acp): route Zed thoughts to reasoning + polish tool/context rendering

[teknium1]

Salvage of #18578 onto current main. All 7 commits cherry-picked from @HenkDz with authorship preserved.

Summary

Zed (and other ACP clients) now show provider reasoning in the thought pane instead of Hermes' kawaii waiting strings, get a live context-usage indicator, and render ~35 tool types as human-readable panes instead of raw JSON.

Changes

• acp_adapter/server.py: thinking_callback=None; route provider reasoning deltas via reasoning_callback; stream assistant response through stream_delta_callback and skip the duplicate final_response send when already streamed.
• acp_adapter/server.py: emit ACP usage_update (context size + estimated used tokens) after new/load/resume session and every prompt; powers Zed's circular context indicator.
• acp_adapter/server.py: /context slash command now shows provider, token pressure, and compression-threshold guidance.
• acp_adapter/server.py: session/load and session/resume replay also reconstructs tool-call start/complete events so loaded threads look like the original.
• acp_adapter/tools.py: polished rendering for ~35 tool types (todo, read_file, search_files, execute_code, skill_view/list/manage, web_search, web_extract, terminal, process, browser_, kanban_, feishu_, ha_, yb_*, cronjob, send_message, delegate_task, etc.); raw_output=None on polished tools so Zed doesn't double-show a raw accordion.
• Tests: +456 lines across tests/acp/test_server.py, test_tools.py, test_mcp_e2e.py.

Validation

• scripts/run_tests.sh tests/acp/ -q → 206 passed
• All 7 contributor commits cherry-picked cleanly onto current main with authorship preserved (rebase-merge this PR).

Closes

Closes #18578. Credit to @HenkDz for the entire implementation.