[TW-4734] refactor(cli): reduce code duplication across commands and adapters

[qasim-nylas]

Summary

• Centralize repeated status-to-color mapping into common.StatusColor() / StatusIcon() / ColorSprint(), replacing duplicate functions in scheduler, webhook, and notetaker packages
• Add common.SetupPagination() with explicit PaginationMode (SinglePage / WithCap / All) to eliminate duplicate limit/maxItems resolution logic across list commands
• Add common.NormalizePageSize() and FetchCursorPages() to reduce cursor-based pagination boilerplate
• Extract dashboard.setDPoPProof() from duplicate blocks in doPostRaw() and doGetRaw()
• Add testutil.WriteJSONResponse() — goroutine-safe, buffer-first encoding with proper 500 on failure — for the JSON response pattern repeated 186 times across 38 test files
• Consolidate email list command into shared fetchListMessages() / applyListFolderFilter() / resolveListPagination()
• Clean up CLAUDE.md: remove git push/commit rules, add shared helper learnings, reduce redundancy

Changed Files

New files (7)

File	Purpose
common/status.go	StatusColor, StatusIcon, ColorSprint — 17 status values
common/status_test.go	29 test cases
dashboard/http_test.go	13 test cases (DPoP, error parsing, envelope, integration)
calendar/events_list_test.go	New test coverage for calendar list
contacts/list_test.go	New test coverage for contacts list
email/list_test.go	New test coverage for email list
webhook/render_test.go	New test coverage for webhook rendering

Modified files (16)

File	Change
common/pagination.go	Added SetupPagination, PaginationMode, NormalizePageSize, FetchCursorPages
common/pagination_test.go	8 new test cases for pagination helpers
dashboard/http.go	Extracted setDPoPProof() from 2 duplicate blocks
testutil/helpers.go	Added WriteJSONResponse() with buffer-first encoding
testutil/helpers_test.go	5 test cases including encode-failure path
scheduler/bookings.go	Removed getStatusColor() + inline switch → common.ColorSprint()
webhook/list.go	Removed getStatusIcon() → common.StatusIcon()
webhook/show.go	Refactored to use displayWebhookDetails() + common.StatusIcon()
webhook/update.go	getStatusIcon() → common.StatusIcon()
webhook/webhook_advanced_test.go	Updated to use common.StatusIcon()
notetaker/list.go	Simplified formatState() from 22 lines to 7 via common.StatusColor()
contacts/list.go	Manual pagination → common.SetupPagination()
email/list.go	Consolidated into resolveListPagination, fetchListMessages, applyListFolderFilter
email/search.go	Uses NormalizePageSize() and FetchCursorPages()
calendar/events_list.go	Uses SetupPagination() and FetchCursorPages()
CLAUDE.md	Removed git push/commit rules, added shared helper learnings, trimmed sections

Stats

• 22 files changed — 7 new, 15 modified
• ~1,558 lines added, ~326 removed
• Net reduction in duplicate code; new lines are mostly tests

Test plan

• make ci passes (fmt, vet, lint, unit tests, race detection, security, vuln, build)
• All new helpers have dedicated unit tests (55+ new test cases)
• Existing tests unbroken — verified TestFetchMessages, TestFormatState, StatusIcon_* etc.
• nylas email list --all pagination behavior preserved (3-mode PaginationMode)
• testutil.WriteJSONResponse encode-failure returns HTTP 500 (not original status)
• Race detection clean on all 8 affected packages

JIRA: TW-4734

[AaronDDM]

LGTM 👍