feat(slack): let bare readers inspect the bot’s recent run

[Shashankss1205]

After a bot run, bare metrics, viz, replay and trace now select a recent trace and state exactly which path and run id were selected. Remember completed traces per channel in a thread-safe bot-local history; fall back to the newest trace under slack-runs/ in a new channel or after restart, and disclose that fallback.

Explicit arguments keep their current behavior. Resolved arguments pass the existing confinement/allowlist gate; empty history, corrupt traces and multi-run ambiguity produce actionable refusals. diff keeps its explicit comparison baseline. Channel history is process-local, as documented.

Add 17 regression checks, including the real demo stage0 → metrics subprocess flow, channel selection and symlink confinement; update the Slack cookbook and selected-test figure. The pre-integration behavior fails 13 new checks. Focused Slack/documentation checks: 151 passed. The final integrated tree through #143 passes 2,395 tests on both Python 3.12 and 3.13 locally; 13 skipped and 13 paid tests excluded. Ruff/diff checks and all 133 installed-wheel module imports pass. GitHub CI results are recorded in the review before merge.

No Slack credentials, network connection or paid model calls are used by the tests.

Fixes #49.

[Shashankss1205]

Evaluation of 4073e86: bare readers disclose the inferred trace/run and prefer per-channel completed history, with an explicit workdir fallback. Typed reader arguments keep their existing behavior. Inferred arguments re-enter the admission gate; candidate paths are confined before reads, corrupt newest traces do not silently select an older answer, and multiple runs require an explicit choice. Channel history is process-local as documented.

Validation: 17 new checks pass, including demo stage0 followed by metrics through the real CLI, missing history, channel isolation, malformed traces and escaping symlinks. The focused Slack/documentation run passes 151 tests. Full integrated local suite: 2,388 passed, 13 skipped, 13 paid tests deselected. Ruff/diff checks and all 133 installed-wheel module imports pass. GitHub CI is pending; merge after #140 and successful checks.

No blocking code findings. diff correctly retains an explicit comparison baseline.

[Shashankss1205]

Final merge check for 4073e86: all GitHub CI test jobs (Python 3.12, 3.13 and 3.14), lint, distribution validation and the live-test guard passed. #140 is merged; the remaining diff contains only the five Slack-related files. The reviewed head is unchanged, with no unresolved review threads or requested changes. Merging with ancestry preserved for #143.