Clarify TUI sampling semantics and preserve socket baselines

[zhongwencool]

Summary

Clarify the measurement contract in the interactive Home, Sockets, and System views without changing their memory data sources or the versioned CLI response schema.

• Distinguish current values, cumulative Reds total, signed change columns, and Reds/s calculated from actual monotonic elapsed time.
• Show warming up instead of lifetime totals in first-window results. Keep missing samples, counter resets, and pause/resume visible; preserve negative memory/heap/queue changes.
• Preserve socket sampling baselines across sorting, paging, and refresh changes. Key baselines by socket identity, clear them after failed enumeration, and fence updated row mappings before accepting a selection.
• Keep the developer-facing recon:proc_count(...) / recon:proc_window(...) expressions. Prefer a single navigation/status row, hide zero missing/reset counts, and wrap without truncating important status on narrow terminals.
• Replace the ambiguous delta glyph with change / chg, distinguish socket window counters from lifetime maxima, and explicitly label Home's used memory versus System's allocated memory.
• Document the semantics and add regression tests for real UDP deltas, missing/reset samples, socket identity, pause/resume, baseline preservation, and terminal widths.

CI and local runtime follow-up

• Pin the OTP 29 test job and Mix job to OTP 29.1.1, and use the same version as the OTP 26 cross-version target.
• Retain OTP 26-28 compatibility coverage, existing check names, and major-version release artifacts.
• Lower the Codecov project target to 95%; keep the patch target at 50% and both thresholds at 0%.
• Upgrade the local mise global Erlang default to OTP 29.1.1. This machine-local change is not a repository runtime pin; the existing Elixir configuration is unchanged.

Validation

Rebased onto current main (30bfc1a) before final validation.

• mise exec -- rebar3 eunit — 811 tests passed on the new default OTP 29.1.1.
• mise exec -- rebar3 as ci check (OTP 29.1.1) — passed compilation, lint, formatting, xref, Dialyzer, and HTML/Markdown/EPUB documentation generation.
• mise exec -- scripts/escript-smoke.sh (OTP 29.1.1) — 17 cases passed, including remote TUI cleanup on stdin EOF.
• rebar3 fmt --check and git diff --check — passed.
• Captured live terminal output verified heap count/window switching, warm-up, and measured sample timing; automated rendering tests cover wide and narrow layouts.

The former OTP 28.0.2 default had an ExDoc re:import/1 incompatibility. The local default is now OTP 29.1.1, and the complete quality check, including ExDoc, passes without a per-command version override. Both YAML files were parsed and their OTP selection, stable check/artifact names, upload gates, and coverage targets were validated.

Scope and compatibility

• No CLI schema changes, release, deployment, or main-branch write.
• This builds on the merged System distribution changes rather than replacing them.
• Socket reconnection identity is covered by fixtures; no new manual remote reconnect acceptance claim is made.
• Hosted CI and cross-OTP acceptance are separate from the local checks above.

[codecov]

Codecov Report

❌ Patch coverage is 94.38202% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.81%. Comparing base (30bfc1a) to head (4d7e3ae).

Files with missing lines	Patch %	Lines
src/observer_cli_socket.erl	90.90%	8 Missing ⚠️
src/observer_cli_lib.erl	92.30%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
- Coverage   97.85%   97.81%   -0.05%     
==========================================
  Files          24       24              
  Lines        7939     8064     +125     
==========================================
+ Hits         7769     7888     +119     
- Misses        170      176       +6     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.