fix(gh-copilot): update Copilot metrics endpoints & schemas to latest…

[bujjibabukatta]

Closes #8964

Summary

The gh-copilot plugin pins the correct Copilot metrics API version
(2026-03-10) but is only partially implemented against it: several
response fields are dropped on extract, org-level rows lose their
identity, three endpoints aren't called at all, and a response-body
bug silently zeroes out both the enterprise and user report collectors.

Bugfixes

Double-read bug (2 occurrences). parseRawReportResponse and
parseUserMetricsReportResponse each read res.Body once directly,
then again inside parseReportMetadataResponse. The second read
always came back empty, so meta was always nil and every
enterprise/user report was silently discarded — no error, no rows.
Fixed by reading once in both places.

Org identity. ExtractOrgMetrics hardcoded EnterpriseId: "" and
never set OrganizationId, so org-level rows in the shared daily
metrics table had no identity of their own. Now stamps
OrganizationId from the report (falling back to the connection's
configured org), and passes EnterpriseId through instead of forcing
it blank.

Field gaps

Field	Where
daily/weekly/monthly_active_copilot_cloud_agent_users	enterprise/org daily metrics
used_copilot_coding_agent, used_copilot_cloud_agent	per-user daily metrics
ai_adoption_phase / totals_by_ai_adoption_phase	new _tool_copilot_metrics_by_ai_adoption_phase table
pull_requests.copilot_suggestions_by_comment_type	JSON blob column (small cardinality, not worth a normalized table yet)
totals_by_cli.last_known_cli_version, .avg_tokens_per_request	shared CopilotCliMetrics

ai_adoption_phase field names (including the 2026-07-07 review-cycle
fields and 2026-06-26 total_pull_requests_merged) were checked
against GitHub's changelog posts.

Missing endpoints

Implements enterprise-28-day/latest, organization-28-day/latest,
users-28-day/latest. These are single "latest" snapshot calls (no
day param, unlike the -1-day reports) whose payload wraps entries in
a day_totals[] array. Reuses the existing enterpriseDayTotal/
userDailyReport shapes for the entries; writes to new, separate
tables so this cadence can't silently overwrite -1-day rows for the
same (connection, scope, day). Per-IDE/feature/language breakdowns
are out of scope for 28-day data in this pass — the -1-day breakdowns
already cover those dimensions.

⚠️ Needs verification before merge: the day_totals[] envelope
shape is inferred from GitHub's endpoint naming/docs, not a captured
sample response. There's a JSONL fallback for robustness, but please
check against a real payload if you have API access.

Migrations

• 20260720_add_copilot_metrics_gaps_v2.go — new columns + AI
  adoption phase table
• 20260720_add_copilot_28day_reports.go — the two new 28-day tables

Migration struct field names were cross-checked against the real
model structs field-by-field to make sure AutoMigrateTables targets
the right columns.

Testing

• go build ./plugins/gh-copilot/...
• go vet ./plugins/gh-copilot/...
• go test ./plugins/gh-copilot/...
• Migration dry run against a scratch DB
• Manual collection run against a real connection — confirm
  non-empty daily metrics tables (regression test for the
  double-read bug)
• Verify day_totals[] shape against a real 28-day report response

[bujjibabukatta]

Hi @klesh could you please review and approve pull request?