Replace template CI/CD with branch-scoped self-publishing model

[ptr727]

Ports the branch-scoped self-publishing CI/CD from ptr727/LanguageTags, replacing the ProjectTemplate two-phase model. main publishes stable releases and develop publishes prereleases; each branch publishes itself when a shipped input changes. Utilities has no codegen, so the generator workflows and merge-bot codegen job are omitted.

Workflows

• Remove build-datebadge-task.yml, build-nugetlibrary-task.yml, get-version-task.yml.
• Add validate-task.yml (unit tests + CSharpier / dotnet format style / markdownlint / cspell / actionlint).
• Rework build-release-task.yml (NBGV, keyless OIDC NuGet/login push, flat Utilities.7z asset), publish-release.yml (push/dispatch self-publisher with a shipped-input inclusion list), test-pull-request.yml (validate + smoke-build + Check pull request workflow status job aggregator), and merge-bot-pull-request.yml (Dependabot auto-merge only).

Config and docs

• Add WORKFLOW.md (canonical CI/CD spec, codegen sections removed) and repo-config/ (rulesets + settings as code, delete_branch_on_merge off).
• Add cspell.json as the single spell-check source; reconcile AGENTS.md, CODESTYLE.md, .github/copilot-instructions.md, .github/dependabot.yml, .vscode/tasks.json, and Utilities.slnx.
• Bump version floor 3.5 -> 3.6; refresh README.md and HISTORY.md.

Verified locally: actionlint, markdownlint, cspell, YAML/JSON parse, bash -n configure.sh, EOL per .editorconfig, and Husky clean-compile.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Replaces the repo's CI/CD pipeline with a branch-scoped self-publishing model: main publishes stable releases, develop publishes prereleases, and publishes are triggered only by shipped-input changes (or manual dispatch). It also codifies the workflow contract and required GitHub configuration as documentation + config-as-code.

Changes:

• Introduces a new workflow architecture: reusable validate-task, ref-scoped CI on push, and a self-publishing publish-release triggered by shipped-input path inclusions.
• Reworks the release build to use a single build/release task with NBGV outputs threaded through, OIDC NuGet publishing via NuGet/login, and a flat Utilities.7z release asset.
• Adds/updates repo documentation and configuration artifacts (WORKFLOW.md, repo-config/, cspell.json) and bumps the version floor to 3.6.

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
WORKFLOW.md	Adds the canonical CI/CD contract, architecture, and audit methodology for workflows and repo configuration.
version.json	Bumps version floor from 3.5 to 3.6.
Utilities.slnx	Updates solution items to include new docs/config and new workflow; removes deleted workflows.
Utilities.code-workspace	Removes embedded CSpell word list in favor of repo-root cspell.json.
repo-config/settings.json	Codifies repository settings (merge methods, auto-merge, delete-branch-on-merge off).
repo-config/ruleset-main.json	Adds config-as-code for the main branch ruleset (merge-only, required check, signatures).
repo-config/ruleset-develop.json	Adds config-as-code for the develop branch ruleset (squash-only + linear history, required check, signatures).
repo-config/README.md	Documents repo-config purpose, usage, and lockstep requirements for required-check renames.
repo-config/configure.sh	Adds an idempotent apply/check script to audit and enforce repo settings/rulesets/secrets presence.
README.md	Updates project README to reflect new distribution links, badges, and CI/CD/release model summary.
HISTORY.md	Adds v3.6 release notes focused on CI/CD changes and new workflow artifacts.
cspell.json	Adds a centralized CSpell configuration and dictionary.
CODESTYLE.md	Updates coding-style guide to align with the new validation model (CI lint gate + cspell.json).
AGENTS.md	Refactors agent guidance to point to WORKFLOW.md for CI/CD and repo-config for enforced GitHub settings.
.vscode/tasks.json	Cleans up task header comments and clarifies which tasks form the clean-compile set.
.github/workflows/validate-task.yml	Adds reusable validation task: unit tests + CSharpier/dotnet-format/markdownlint/cspell/actionlint.
.github/workflows/test-pull-request.yml	Reworks CI to run on push (head-resolved reusable workflows) and produces the required aggregator job.
.github/workflows/publish-release.yml	Reworks publisher to be branch-scoped and shipped-input-triggered; gates publish on validate-task.
.github/workflows/merge-bot-pull-request.yml	Simplifies merge-bot to Dependabot auto-merge only (no semver-major exception), with App-token strategy.
.github/workflows/get-version-task.yml	Removes old reusable version task (inlined into build-release-task).
.github/workflows/build-release-task.yml	Reworks the core build/version/publish logic (NBGV, OIDC NuGet push, Utilities.7z, artifact lifecycle).
.github/workflows/build-nugetlibrary-task.yml	Removes old build task (superseded by build-release-task).
.github/workflows/build-datebadge-task.yml	Removes date-badge workflow/task (no longer part of the contract).
.github/dependabot.yml	Updates rationale comments; preserves dual-target main/develop Dependabot strategy.
.github/copilot-instructions.md	Minor wording updates to reflect CODESTYLE.md section framing.