perf(clients): bound routine queries by default

[mfacenet]

Summary

• cap routine queries at 100 commits by default while preserving an explicit 0 for exhaustive scans
• expose a per-call max_commits override to MCP clients and keep MCP diff retrieval explicitly opt-in
• reduce GitHub and GitLab pagination once the truncation-probe budget is satisfied, including repo and org/group scans
• document the new defaults and add regression coverage for config, MCP, and provider behavior

Why

Routine queries should avoid unnecessary provider requests, rate-limit pressure, and token-heavy MCP output without weakening the exact Truncated result contract.

Testing

• go -C tools tool task ci
• go -C tools tool task test-cover-check
• graphify update . (894 nodes, 1,667 edges; generated output remains ignored by repository policy)

[Copilot]

Pull request overview

This PR updates sting’s default behavior to cap routine queries at 100 commits (while preserving 0 as “unlimited”), and reduces upstream pagination/work once the cap is satisfied. It also refines MCP semantics so diff retrieval is explicitly opt-in per call and adds a per-call max_commits override for MCP clients.

Changes:

• Set default max_commits to 100 across config, CLI flags, docs, and examples; keep 0 as the explicit exhaustive-scan escape hatch.
• Make MCP include_diffs default to false when omitted (independent of server config), and add MCP max_commits as a per-call override.
• Reduce GitHub/GitLab pagination and stop repo/org/group enumeration once the remaining commit budget is exhausted; add regression tests for these behaviors.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
README.md	Documents the new default cap and clarifies MCP diffs are opt-in.
internal/mcpserver/server.go	Adds max_commits to MCP input; makes omitted include_diffs default to false for MCP calls.
internal/mcpserver/getcommits_test.go	Adds tests for MCP max-commit override and diffs-default-off behavior.
internal/cli/root.go	Changes CLI default --max-commits from unlimited to config.DefaultMaxCommits.
internal/cli/cli_test.go	Asserts loaded config defaults include the new default max commits.
config/config.go	Introduces DefaultMaxCommits = 100; updates default config and validation.
config/config_test.go	Adds validation coverage for negative max_commits.
config/resolve.go	Adds per-request MaxCommits override handling and validation.
config/resolve_test.go	Adds coverage for default max commits and request override semantics (including explicit 0).
config.example.yaml	Updates example config to show the new default max_commits: 100.
ghclient/ghclient.go	Bounds page sizes and stops org/repo pagination early once the commit budget is satisfied.
ghclient/collect_test.go	Adds regression test ensuring org repo pagination stops once MaxCommits is reached.
gitlabclient/gitlabclient.go	Bounds page sizes and stops group/project pagination early once the commit budget is satisfied.
gitlabclient/gitlabclient_test.go	Adds regression test ensuring group project pagination stops once MaxCommits is reached.