NBK-175: remove redundant DDSQL time-series command

[nmuldavin]

Linear

NBK-175 — https://linear.app/datadoghq/issue/NBK-175/pup-remove-ddsql-time-series

Outcome

pup ddsql time-series is hard-removed. Remaining examples use the general pup ddsql table command without prescribing a migration-specific row limit.

Scope

• Remove the redundant clap variant, dispatch arm, implementation, and parity-harness entry.
• Replace the stale positive parse test with a negative unknown-subcommand regression test.
• Remove the command from DDSQL help and command documentation.
• Keep the NBK-161 public v2 execution implementation unchanged; this branch is stacked on PR NBK-161: migrate DDSQL execution to public v2 API #785.

Acceptance

• pup ddsql time-series exits 2 with a clear unrecognized subcommand 'time-series' error.
• Remaining DDSQL examples use pup ddsql table without prescribing a migration-specific row limit.
• No pup ddsql time-series command reference remains in the requested docs or agent guides.
• The stale positive parse test and parity-harness entry are removed.

Validation

• cargo fmt --check — passed.
• cargo clippy --all-targets -- -D warnings — passed.
• cargo test -- --test-threads=1 — 1,903 passed, 0 failed on the rebased stack.
• python3 -m py_compile scripts/test_harness.py — passed.
• ./target/debug/pup --no-agent ddsql time-series --query 'SELECT 1' — exited 2 with the expected unknown-subcommand error.
• ./target/debug/pup --no-agent ddsql --help — lists table, spec, and schema; no time-series reference remains.

Not run / automation gaps

• Cross-platform compilation is left to CI.

Material deviations and decisions

• Breaking change: pup ddsql time-series is removed without a compatibility alias.
• NBK-161 / PR NBK-161: migrate DDSQL execution to public v2 API #785 merged as 4ed3b64; this branch is rebased onto that merge and the PR diff now contains only NBK-175 changes.

Remaining work or conditions

• CI must rerun after the rebase.
• Keep the PR draft until explicit human approval to mark ready for review.