feat: Implement Slack export importer and enhance README documentation for historical context recovery

.opencode/commands/slack-import.md

@@ -0,0 +1,59 @@
+---
+description: Import a historical Slack export and refine workspace memory from it
+---
+
+Use a Slack export as a historical context source for the workspace.
+
+Interpret this as historical recovery, not as current truth and not as model training.
+
+Inputs:
+
+- `$ARGUMENTS` may contain an export path, channel names, or date filters
+- if no explicit path is given in the arguments, use `FIDELITY_SLACK_EXPORT_PATH` when available
+- otherwise, if `archives/slack/export/` exists, use it as the default import source
+- if no channels are specified, auto-detect channels whose folder names start with `fidelity`
+- if no message limit is specified, auto-tune message selection based on archive size
+
+First, run the importer:
+
+!`if [ -n "$ARGUMENTS" ]; then python3 scripts/slack/import_slack_export.py $ARGUMENTS; elif [ -n "$FIDELITY_SLACK_EXPORT_PATH" ]; then python3 scripts/slack/import_slack_export.py --export-path "$FIDELITY_SLACK_EXPORT_PATH" --channel-prefix fidelity; elif [ -d archives/slack/export ]; then python3 scripts/slack/import_slack_export.py --export-path archives/slack/export --channel-prefix fidelity; else echo "Provide Slack import arguments, set FIDELITY_SLACK_EXPORT_PATH, or place an extracted export in archives/slack/export."; fi`
+
+Read:
+
+@ai/AGENTS.md
+@ai/context/project.md
+@ai/context/people/index.md
+@ai/context/people/manager.md
+@ai/state/current.md
+@ai/state/work-items.md
+@knowledge/agent-memory-rules.md
+@knowledge/memory-promotion-rules.md
+
+Imported summary, if present:
+
+!`if [ -s scripts/slack/generated/slack_summary.md ]; then cat scripts/slack/generated/slack_summary.md; else echo "No Slack summary generated."; fi`
+
+Imported Slack context, if present:
+
+!`if [ -s scripts/slack/generated/slack_context.jsonl ]; then cat scripts/slack/generated/slack_context.jsonl; else echo "No Slack context generated."; fi`
+
+Instructions:
+
+- treat the Slack archive as historical evidence
+- assume this may be a large multi-year export
+- promote durable project-relevant context automatically when confidence is high
+- prefer promoting:
+  - repeated Jira IDs and titles still relevant to current understanding
+  - durable role/person associations
+  - recurring architecture or debugging patterns
+  - past approvals or decisions that still matter
+- prioritize high-signal messages such as Jira references, approvals, scope changes, root-cause notes, points, and persistent technical constraints
+- avoid promoting outdated daily status unless it changes current understanding
+- update existing memory when the archive clarifies or corrects it
+- if historical facts are ambiguous or likely outdated, summarize them as archived context instead of promoting them
+
+Return:
+
+1. What was imported
+2. Which files were updated
+3. Which historical facts were promoted or intentionally left as archive-only context