docs: document DeepSWE harness versions and release timing

[ZeroPoint95]

What changed

The DeepSWE comparison published scores without identifying the harness releases, making it unclear whether its OpenCode result measured 1.x or 2.x.

• Document the nine competing harness versions with recorded source revisions, public release dates and links; explicitly identify OpenCode 1.18.30 and explain the patch-release timing for Claude Code and DeepSeek Harness.
• Identify senior-dev through its public integration commit dd0fcc654 (#1488) and first stable codeaf release v0.5.0. Explain that these establish public lineage for the agent measured before integration.
• Add a five-column versions.csv beside arms.csv: harness, version, source revision, release publication timestamp and source URL. The senior-dev row uses the public integration/release references; the other rows identify the tested versions.
• Link DeepSWE from the benchmark index, correct the campaign dates to September 10–12 UTC, and add the required change entry. Published scores are unchanged.

Fixes #1841.

How it was checked

• Matched the nine competing version identifiers to 113 unique saved task records per arm; checked release-timing claims against the records and upstream release metadata.
• Confirmed that integration commit dd0fcc654 is contained in v0.5.0 and absent from the preceding stable v0.4.1; checked the v0.5.0 release timestamp and merge reference against GitHub.
• Checked the five-column CSV against all ten results rows and the documentation; validated links and scanned the changes for private references and local paths.
• make pr-ready and git diff --check pass; no Go or module files changed.