docs: simplify documentation structure and troubleshooting

[Hou (SciencePotato)]

Summary

• Keep the README diagram-first, with the original single-region image. Move the customer walkthrough to docs/GETTING-STARTED.md and retain the safety/eligibility gates.
• Add a nested README table of contents, concise features and requirements, categorized deployment/operations/development guidance, optional designs, and support routes. Use docs/README.md as the complete task index.
• Give long guides direct section routes. Separate guided customer setup from local/manual development in all three runtime READMEs.
• Reshape troubleshooting around the failing stage, concrete checks, safe fixes, and expected results. Keep all original searchable error cases and non-destructive recovery rules.
• Extract the detailed event/identifier schema into docs/LOGGING.md; keep CONTRACT.md#application-logs as a useful compatibility link. Keep precise API, setting, status, cache, and runtime details in their canonical references.
• Tighten the long Front Door and identity-monitoring runbooks, runtime cache/configuration explanations, onboarding, setup prerequisites, and recovery guidance without removing their safeguards or exact examples.
• Present regional resiliency and BCDR as a positive progression from the validated single-region baseline, with the Front Door context located in the resiliency section rather than the technical introduction.
• Use natural, direct openings and handoffs across the landing page, task index, setup, operations, runtime, contract, and advanced-design guides.
• Present extensibility as Advanced topics and production gaps as Production-readiness considerations. Explain the isolated test environment in plain language and state authentication, activation, and timeout safeguards as supported next actions rather than disconnected prohibitions.
• Replace slogan-like and overexplained headings with short literal labels such as Architecture, Monitoring, HTTP contract, Provider fallback, and C# implementation. Keep the explanation in the paragraph below and preserve the previous public anchors.
• Remove rhetorical questions, conversational prompts, contractions, and phrases such as “looking for,” “want to,” and “your team.” Use neutral task labels and factual transitions throughout all customer, operations, runtime, and reference guides.
• Apply three complete readability passes across all 19 pages: shorten multi-clause sentences, replace formal wording with simpler terms, and frame supported capabilities before necessary safeguards.
• Remove another full round of repeated introductions, link descriptions, deployment explanations, and runtime boilerplate across all 19 pages. Keep exact commands, examples, settings, error strings, tables, and safeguards.
• Consolidate repeated prose without changing commands, KQL, runtime code, configuration, infrastructure, or any image bytes.

Full structure pass

Reviewed every tracked guide, not only the earlier three-file reduction. The cost-report script, permissions, and estimate safeguards remain unchanged; only its surrounding explanation is simpler. Hosting-cost work remains separate.

The new index replaces duplicated reference catalogs. Root guidance now routes each goal directly to its starting page, while the documentation index groups the remaining guides by task. Setup permissions, certificate choices, renewal, and rollback stay in the setup reference. Provider credentials, IDs, acceptance checks, and exact Easy Auth settings stay in customer configuration. Runtime guides link to those rules while retaining their local examples, source maps, binding differences, and credential lifecycles. Operational monitoring points to collection diagnostics and the focused log schema rather than repeating them.

The BYOT page remains provider-neutral and instructions-only. Identity monitoring remains beginner-first with no inline KQL. Advanced regional/fallback designs keep their detailed capacity, uncertainty, privacy, abort, and restoration safeguards.

Measured reduction

The full structural pass reduces all documentation from 52,664 to 43,886 whitespace-delimited Markdown words, a net reduction of 8,778 (16.7%), including both new pages, expanded landing-page navigation, the BCDR section, and the complete prose review. The final concise pass removes 4,516 words from the previous published head across all 19 pages. Counts are measured against the previously published PR54 head c2827d8f8db56b3248fd5796a18c50db78b0ef25, not a selectively chosen page.

Across the complete PR, the root README changes from 1,997 to 406 words. It now follows the reference repository's layered structure without moving the detailed setup walkthrough back into the landing page. Precise tables and examples are deliberately retained.

Per-page structural-pass counts and relocation accounting

Page	Before	After
README.md	306	406
TECHNICAL.md	3,055	2,315
docs/APPLICATION-INSIGHTS.md	2,466	2,255
docs/BRING-YOUR-OWN-PROVIDER.md	1,827	1,612
docs/CONTRACT.md	6,566	5,016
docs/COST-CALCULATOR.md	1,252	1,060
docs/FRONTDOOR.md	5,137	4,153
docs/GETTING-STARTED.md	2,005	1,315
docs/LOGGING.md (new focused reference)	0	1,128
docs/MONITORING.md	4,854	4,503
docs/MULTI-PROVIDER-IMPLEMENTATION.md	2,526	2,294
docs/ONBOARDING.md	3,752	3,056
docs/README.md (new task index)	0	210
docs/SIGN-IN-MONITORING.md	4,766	4,141
dotnet/README.md	1,431	824
javascript/README.md	1,329	678
python/README.md	1,208	651
setup/docs/README.md	6,159	5,149
setup/docs/Troubleshooting.md	4,025	3,120
Total	52,664	43,886

Counts include markup, links, code, and tables consistently. The contract's reduction includes relocating its logging section; the new logging page is included in the after-total, so relocation is not counted as deletion.

Validation

• Checked 753 local and external links, anchors, and image references across all 19 Markdown pages; every local target and anchor resolves, and every guide is reachable from the task index.
• Preserved all previous public heading/explicit anchors, all 46 fenced command/code/query examples, and all existing technical table rows. The old getting-started reference catalog is replaced by the index with every destination retained.
• Preserved every inline field/event identifier from the extracted logging section; reviewed its semantics against the original prose and the JavaScript/Python/.NET logging sources.
• Compared all 16 original images byte-for-byte with upstream base, including both architecture PNGs. No images added.
• Rendered and visually reviewed all 19 pages at exact 1280px/390px widths, including the landing page, setup, troubleshooting, runtimes, monitoring, identity, cost, contract, multi-region, and provider-fallback pages. No broken images or horizontal overflow; 20 click-through preview journeys passed.
• Reviewed retained details, customer next actions, operational safeguards, and PR53 overlap in an artifact inventory covering every guide.
• Passed git diff --check.

Local previews approximate GitHub styling rather than testing its hosted renderer. Existing wide tables/code scroll within their containers; the preserved architecture image needs its full-size link for small labels. External URL availability was not checked. No runtime suite, live query, Azure sign-in/deployment, provider send, or paid action was run. No repository tooling/dependencies were added.

Integration

Base: upstream main, ce68ee2649d8e4ab64e00c4abece33e939cdfa9c. No unmerged commits from #53 are imported, and #50's hosting-cost work is not duplicated.

#53 shares TECHNICAL, BYOT, Front Door, configuration, runtime READMEs, and setup-reference files. The earlier diagram relocation still overlaps TECHNICAL's image section; this structural continuation leaves that section unchanged. When integrating, place #53's unique screenshot/sequence guidance alongside the new task navigation rather than restoring repeated overview prose. All original images remain unchanged.

No merge or Agent merge is requested.