[mkajander]

Summary

• add bbt pr summary [<id>] with human, JSON, and quiet output
• derive mergedAt from Bitbucket PR activity instead of guessing from updated_on
• emit mergedAt: null explicitly when no reliable merge timestamp exists

Testing

• dotnet test

[Copilot]

Pull request overview

Adds a new bbt pr summary command to expose normalized, automation-friendly pull request metrics (including diff stats and an accurate mergedAt), extending the existing pr command suite and updating the Bitbucket contract docs accordingly.

Changes:

• Introduce bbt pr summary [<id>] with human, --json, and --quiet output modes.
• Compute diff stats (files changed / lines added / lines removed) from the PR diff.
• Derive mergedAt from the PR activity log and ensure JSON output includes "mergedAt": null when unavailable.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/Bbt.Core.Tests/Diff/PullRequestDiffStatsCalculatorTests.cs	Adds coverage for diff stats aggregation.
tests/Bbt.Core.Tests/Bitbucket/PullRequestSummaryModelTests.cs	Verifies summary mapping and mergedAt null-serialization behavior.
tests/Bbt.Core.Tests/Bitbucket/PullRequestActivityAnalyzerTests.cs	Adds coverage for merged timestamp derivation from activity updates.
src/Bbt/Program.cs	Registers the new pr summary subcommand.
src/Bbt/Models/PullRequestModels.cs	Introduces PullRequestSummary model with non-ignored MergedAt.
src/Bbt/Infrastructure/ModelMappers.cs	Adds mapping to PullRequestSummary, including review state counting.
src/Bbt/Commands/Pr/PrSummaryCommand.cs	Implements the pr summary command including diff parsing and mergedAt resolution.
src/Bbt/Commands/Llms/LlmsCommand.cs	Documents the new command in the LLM command inventory output.
src/Bbt.Core/Diff/PullRequestDiffStatsCalculator.cs	Adds calculator for diff-based summary stats.
src/Bbt.Core/Diff/Models.cs	Adds PullRequestDiffStats record.
src/Bbt.Core/Bitbucket/PullRequestActivityAnalyzer.cs	Adds logic to select latest MERGED activity timestamp.
src/Bbt.Core/Bitbucket/Models/BitbucketPullRequestActivity.cs	Adds models for the PR activity endpoint payload.
src/Bbt.Core/Bitbucket/Models/BitbucketPullRequest.cs	Adds comment_count mapping.
src/Bbt.Core/Bitbucket/BitbucketClient.cs	Adds client method to list PR activity.
docs/contracts/bitbucket-cloud-v0.1.md	Updates pinned contract with activity endpoint and fields used by pr summary.
README.md	Documents bbt pr summary usage and behavior (notably mergedAt).

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