Ship the 8 + 3 tables with setup; fix the cache preflight and quality slider (0.2.0)

[KBRASK]

Follow-up to #60 after review and testing on Windows. Builds on #61 (the first-generation fix and the launcher wordmark), so merge #61 first.

Default 8 + 3 works out of the box

• Setup always installs the four three-step refinement tables (332 MiB), so the default 8 + 3 also works offline.
• New installations prepare every quality level by default (5.5 GiB more). Existing installations keep their choice in the launcher, the CLI and the ComfyUI setup panel. --no-sampling-caches opts out.
• Tables are added only when a reused cache's weights match the published ones. Source conversions compute their own tables.
• With every level requested, the launcher used to treat the installation as unfinished, so each update or launch reopened the setup review for a 0 GiB plan. It now checks the files and sets up again only while a level is missing.
• Setup downloads the 900 small table files six at a time with verified resumable transfers. Before, each file went through a large-model transfer process two at a time, about half an hour on a fast connection.

Installed files are actually used

• Engine processes receive FREEVIDEO_HOME only, so paths.model_root() meant models/, while setup and the request preflight write to the recorded model folder (models/vdn). The engine therefore never used installed or preflighted sampling tables. It downloaded each one again during the timed run, so "Prepare all quality levels" saved nothing. New installations also downloaded the 690 MB latent upscaler a second time on their first two-pass generation.
• Both now resolve the recorded folder. A copy an earlier version downloaded under models/ stays in use.
• The launcher keeps its DLL directory when parallel source probes start several curl processes at once (follow-up to Repair missing Windows curl automatically and improve diagnostics #53).

Cache preflight before a request

• Reference audio, image + audio, and video-with-soundtrack requests fetch the tables the encoder actually selects. Before, they fetched unused image-to-video tables and then downloaded the right ones during the timed run.
• Downloads run in parallel using the sources ranked at setup. The fixed cost before every request (a speed test of up to 32 MiB per source) is gone. Measured on the t2va three-step table (58 MB): 13.8–15.5 s before, 1.8–2.1 s after.
• A cancel stops every transfer at once.
• A damaged or superseded shared copy is set aside and downloaded again instead of blocking every request.
• Free space is checked first. The ComfyUI console stays quiet.
• The engine reads each table file from whichever folder holds it, so a table split between the cache and the shared folder is never downloaded again.

Quality slider

• Each level is a complete plan: Light is two-pass 8 + 3, and Medium, High and Max are single-pass 12, 16 and 20.
• Editing first-pass steps turns two-pass off only for a committed, valid value, and turns it back on at 8. Ctrl+Enter commits a field being edited before queuing.
• Opening the studio never rewrites a workflow. A saved workflow that already uses another plan shows as Custom.
• Workflows saved with the earlier 8 + 2 default move to 8 + 3 once. A later explicit 8 + 2 is kept.
• Chinese level names (轻量 / 标准 / 精细 / 极致) and 即将推出.
• Estimates now also work on Macs, matched by chip and unified memory.

Other

• Tuned placement profiles also apply to the default version-3 plan.
• Diagnostics keep the optional table counters.
• Version 0.2.0 with bilingual release notes.

Checked

• Full development test suite (1627 tests) against Add quality levels, independent three-step refinement and sharing #60's state: no new failures. Two stale tests now pass after updating them to 8 + 3.
• JS tests: no new failures.
• Installation checks and package builds pass.
• Headless Chromium, English and Chinese: 62 slider and share-card checks. Of the 2 failures in the first round, the Ctrl+Enter one is fixed by this change.
• Live preflight against Hugging Face and ModelScope:
  • reference task selection;
  • a table split across folders;
  • damaged-file recovery;
  • cancel within 0.75 s.
• Windows (RTX 5060 Ti): Fix the first generation after a sampling cache download; show the launcher wordmark #61's build ran the default request end to end. This branch's build is being checked.