docs: update repo/developer/in-app docs and repair the screenshot pipeline for 2.8.0

[jamesarich]

What

Brings documentation current with everything bundled in release/2.8.0 — the repo / agent docs and the hosted + in-app docs under docs/ — and repairs the screenshot pipeline that feeds both the Jekyll site and the in-app docs browser.

Grounded by a source-verified audit of the release branch, then an adversarial accuracy pass over the drafts that caught and corrected 4 over-claims: the App Functions settings entry is actually labeled "System AI" (not "App Functions"); Android Auto emergency alerts are not yet wired (emptyFlow()), so that section was removed; there is no canned-reply list (voice/text reply only); and the Discovery AI summary is not flavor-gated (ships on all Android builds, AI-vs-algorithmic depends on on-device model availability).

Commit 1 — doc content (ced62d911)

Repo / agent docs

• Remove the obsolete git submodule update --init proto-submodule bootstrap (proto is the org.meshtastic:protobufs Maven dep since Replace :core:proto with org.meshtastic:protobufs:2.7.25 #5675) from CLAUDE.md, .skills/project-overview, .skills/new-branch; reword the AGENTS.md "Never Touch Protos" rule.
• README.md: drop the dead core/proto row; add feature/discovery, feature/car, baselineprofile; add a 2.8.0 Features section.

Developer docs (docs/en/developer)

• Remove core:proto / core:api from the module maps; add feature:discovery, feature:car, baselineprofile, screenshot-tests.
• Add the PacketFts FTS5 table to persistence; add a Baseline Profile section to testing; refresh "What's New for Developers"; fix the screenshot task name.

User / in-app / hosted docs (docs/en/user)

Page	Change	Feature
discovery.md	New Local Mesh Discovery scanner section + fix contradictory line	#5275
node-metrics.md	Air Quality metrics (PM1.0/2.5/10, CO₂ severity bands)	#5701
messages-and-channels.md	Full-text message search	#5373
android-auto.md (new)	Android Auto guide	#5633
app-functions.md (new)	App Functions / System AI guide	#5585
desktop.md, user.md	feature-parity rows + What's New entries	—

The two new pages are wired into the in-app docs browser (DocBundleLoader.kt + DocPageIconResolver.kt + 4 string resources). nodes.md already documented msh.to device links (#5714/#5765).

Commit 2 — screenshot pipeline repair + 2.8.0 feature screenshots (1f66dbf87)

A checksum-verified audit of the screenshot pipeline found it substantially broken:

1. In-app images never rendered. Pages reference ../../assets/screenshots/… but ComposeResourceImageTransformer built an unnormalized files/docs/../../… path and silently swallowed the miss — every page in the in-app reader was imageless. Fix: the resolver anchors assets/… links at files/docs/, and a new DocImageWiringTest fails the build if any doc-page image doesn't resolve to a bundled resource.
2. The bundle shipped the wrong directory: ~4 MB of raw unaliased CST renders nobody references, while 9 markdown-referenced images were missing in-app. Fix: docs/assets/screenshots/ (tracked, semantic names) is now the single source for the Jekyll site and the in-app bundle; copyDocsScreenshots refreshes it, copying only alias-mapped light-mode reference images.
3. 6 aliases pointed at the wrong component (telemetric_actions→ElevationInfo, quick_chat→ChannelInfo, detail_local→DeviceListItem, detail_section→AppInfoSection, position→SatelliteCount, environment_metrics→a dark-mode SignalInfo render) and 2 at deleted previews — any regeneration would have clobbered good images with wrong ones. All corrected; missing mappings added. (connections_wifi_* remain manual captures until matching previews exist.)

New deterministic previews with mock data

Wired into screenshot-tests and embedded in the doc pages: discovery preset-result card + dwell progress (feature/discovery, new module dep + manifest entry), air-quality metric cards (feature/node), message search bar (feature/messaging), App Functions settings (feature/settings). Android Auto stays text-only (Car App Library templates aren't Compose).

Drive-by bug fix caught by the new preview

AirQualityMetricsCard (new in 2.8.0, #5701) rendered its timestamp and PM rows stacked on top of each other — SelectableMetricCard's SelectionContainer imposes no layout. Now wrapped in a Column like its environment-metrics sibling, with a timeTextOverride preview seam for deterministic renders.

Verification

• Commit 1: spotlessApply spotlessCheck detekt :feature:docs:allTests green; full PR CI green on ced62d911 (12 pass / 0 fail).
• Commit 2: spotlessApply spotlessCheck detekt :screenshot-tests:updateDebugScreenshotTest + copyDocsScreenshots + validateDebugScreenshotTest (317 screenshot tests) + :feature:docs:allTests (incl. the new DocImageWiringTest) + :feature:node:allTests — all green locally; PR CI running.

Targets release/2.8.0 (not main).

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