Feature set: time granularities, row filters, config file, CSV output, and better help

[lorecanc]

Proposal

I've been using opencode-usage daily and prepared a set of additive features that I'd like to contribute as separate PRs (all are ready, tested, and pass ruff + the existing test suite):

1. #? feat/db-and-no-llm — wire the --db path override through the CLI (it was only consumed by the insights orchestrator via getattr, with no flag to set it) and add --no-llm for data-only insights reports.
2. #? feat/time-granularities — group by minute/hour/week/month in addition to day, plus --weeks N / --months N time windows.
3. #? feat/filters-and-output — row filters (--provider/--model/--agent, repeatable, plus --exclude-provider), --sort cost|calls, a monthly run-rate projection in the summary (also in JSON as run_rate_monthly), and --csv output.
4. #? feat/config-and-commands — optional ~/.config/opencode-usage/config.toml (defaults for period/grouping/sort and [insights] preferred_models for the model picker), providers / models listing commands sourced from opencode models, and a help subcommand with exhaustive documentation.

Notes on cross-PR plumbing

• The Filters dataclass is defined identically in PRs 2 and 3 (the granularity PR forwards the future filter parameter through by_time); git deduplicates the identical hunk at merge time.
• Each PR keeps the existing tests green and adds its own tests; README is updated per PR.

Happy to rework anything to match your preferences (scope, naming, or splitting).

[lorecanc]

The four PRs are up:

• feat(cli,insights): wire --db path override and add --no-llm data-only mode #7 feat(cli,insights): wire --db path override and add --no-llm data-only mode
• feat(cli,db): add minute/hour/week/month granularities and --weeks/--months windows #8 feat(cli,db): add minute/hour/week/month granularities and --weeks/--months windows
• feat(cli,db,render): add row filters, cost sorting, run-rate projection, and CSV output #9 feat(cli,db,render): add row filters, cost sorting, run-rate projection, and CSV output
• feat(cli,config): add config file, providers/models listing, and help command #10 feat(cli,config): add config file, providers/models listing, and help command

All pass the existing suite plus their own tests, and ruff is clean.