159819: cmd: add ghsearchdump and ghweeklysummary r=wenyihu6 a=wenyihu6

Epic: none 
Release note: none

---
**ghsearchdump**


---
**cmd/ghweeklysummary: add tool for generating weekly PR summaries**

```
Example usage:

# Last 1 week
go run ./pkg/cmd/ghweeklysummary --author wenyihu6 --weeks 1

# Specific date range
go run ./pkg/cmd/ghweeklysummary --author wenyihu6 --after 2025-01-01 --before 2025-02-01

# Save to file
go run ./pkg/cmd/ghweeklysummary --author wenyihu6 > weekly_summary.md
```

Release Notes: None
Epic: None

---
**cmd: move kv dev tools under pkg/cmd/kv/**

Move ghsearchdump and ghweeklysummary under pkg/cmd/kv/ for clearer
ownership. This seems okay given we already have pkg/cmd/allocsim.

```
Example usage:

❯ go run ./pkg/cmd/ghweeklysummary --author wenyihu6 --weeks 1

❯ go run ./pkg/cmd/kv/ghsearchdump \
  --search "repo:cockroachdb/cockroach author:wenyihu6" \
  --contribution-after 2025-12-12
tracking contributions from: [wenyihu6]
```



160459: kvserver: add tracing to TestStoreRangeSplitBackpressureWrites r=tbg a=stevendanna

In #160141 we observed this test fail. This test is rather stable but does depend on two goroutines sending batches to the KV server within a 100ms timeout. One suspicion is that very rarely we are too slow and this time-based coordination is not enough.

This test is rather stable and adding more sophisticated coordination will further complicate an already complicated test. Here, I add some tracing that will hopefully allow us to confirm the timing based theory if this ever happens again.

Fixes #160141

Release note: None

160499: pgwire: handle negative scale r=drewkimball,yuzefovich a=dils2k

The node could crash if it received a decimal with a negative scale value. This commit adds a check and returns an error instead.

Epic: CRDB-57539
Fixes: #158884

Release note (bug fix): CockroachDB could previously crash when handling decimals with negative scales via extended PGWire protocol and this has been fixed (an error is returned, similar to PG).

160526: sql: fix TestUnsplitRanges to work with external test tenants r=rafiss a=rafiss

Previously, TestUnsplitRanges was skipped in external test tenant mode because it scanned meta ranges directly and performed AdminSplit/ AdminUnsplit operations that external tenants cannot do.

This commit fixes the test by:
1. Using the system layer's DB for meta range operations (scanning meta ranges, checking sticky bits, splitting ranges) since tenants cannot access meta ranges directly.
2. Using the application layer's DB for table data operations which tenants can access.
3. Granting the CanAdminUnsplit capability to the external tenant so the GC job can unsplit ranges after dropping tables/indexes.

Resolves: #142388
Epic: CRDB-48944

Release note: None

Co-authored-by: Tobias Grieger <tobias.b.grieger@gmail.com>
Co-authored-by: wenyihu6 <wenyi@cockroachlabs.com>
Co-authored-by: Steven Danna <danna@cockroachlabs.com>
Co-authored-by: dils2k <dils.matchanov@gmail.com>
Co-authored-by: Rafi Shamim <rafi@cockroachlabs.com>