Clean up keynote-2 template README & DEVELOP

[bradleyshep]

Description of Changes

Resolve contradictions between keynote-2 README and DEVELOP docs and align them with the codebase.

README.md:

• Use pnpm install and pnpm run demo in Quick Demo (consistency with pnpm workspace)
• Add --concurrency and --alpha to demo options
• Add -- separator to docker compose run bench example
• Fix hardware config punctuation (add comma before "OS:")
• Capitalize "Rust Client" heading
• Fix typos: "bottlnecked" → "bottlenecked", "then" → "than"
• Remove redundant Quick Start section; replace with link to DEVELOP.md for prerequisites and CLI reference

DEVELOP.md:

• Use pnpm run throughout (demo, prep, bench) instead of npm run
• Add Rust to Prerequisites
• Fix connector names in examples (sqlite → sqlite_rpc, postgres → postgres_rpc)
• Update CLI defaults to match methodology (seconds: 1→10, concurrency: 10→50)
• Add explicit list of valid connector names
• Add -- separator to docker compose run bench example; condense to single line
• Fix npm prep → pnpm run prep in Docker instructions

demo.ts:

• Change --concurrency default from 10 to 50 (matches docs and methodology)

cli.ts:

• Change bench defaults from seconds=1, concurrency=10 to seconds=10, concurrency=50 (matches README methodology)

.env.example:

• Comment out USE_DOCKER=1 and SKIP_CONVEX=1 so demo defaults (convex, spacetimedb) work out of the box
• Remove CONVEX_USE_SHARDED_COUNTER

API and ABI breaking changes

None.

Expected complexity level and risk

1 – Documentation and default value changes. No functional changes to core logic.

Testing

• Run pnpm install && pnpm run demo in keynote-2 template
• Confirm DEVELOP.md examples run (e.g. pnpm run bench test-1 --connectors spacetimedb,sqlite_rpc)
• Confirm Docker bench example runs: docker compose run --rm bench -- --seconds 5 --concurrency 50 --connectors convex