docs: explain how Spec Kit uses an agentic SDLC

[mnriem]

Summary

• Add a sourced case study of how Spec Kit uses SDD, feature assessment, bug workflows, conventional automation, and human decisions across the SDLC.
• Trace the incremental adoption of agentic workflows without treating proposed automation as deployed functionality or equating bots with coding agents.
• Link the new guide from the docs homepage, table of contents, and documentation overview.

Evidence and validation

• The guide cites repository workflow sources, contribution policy, release process, and historical PRs/commits; its 46 linked upstream source URLs and 20 dated timeline references were checked.
• Markdown lint passed on the three changed Markdown files. DocFX built the docs and rendered the guide/navigation (with two existing config-glob warnings).
• Documentation only; no executable behavior changed.

AI contribution disclosure

GitHub Copilot (GPT-6 Sol; model ID gpt-6-sol) drafted and revised the documentation, checked sources and rendering, and prepared this commit and PR. Mode: autonomous; reasoning-effort setting not supplied. The contributor provided iterative direction and feedback on the guide. No claim of line-by-line human review or unaided authorship.

[Copilot]

Copilot review overview

🟡 Changes recommended

The guide uses incorrect command names when describing the historical bundler workflow.

Review effort: Balanced
Findings: 1

Open (1)

• Use dotted command names to match historical dogfooding run · New

What changed in this PR

Adds a sourced guide explaining how Spec Kit combines agentic workflows, SDD, conventional automation, and human oversight.

Changes:

• Documents practices across seven SDLC stages and their adoption timeline.
• Adds homepage and navigation links to the guide.
• Updates the documentation overview and homepage date.

File	Description
docs/​guides/​agentic-sdlc.md	Adds the agentic SDLC case study.
docs/​index.md	Promotes the guide on the homepage.
docs/​toc.yml	Adds guide navigation.
docs/​README.md	Lists the new guide.

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[mnriem]

Review-round summary for commit ecb9a5ca: I changed the historical bundler commands to /speckit.plan and /speckit.tasks, matching the linked SDD snapshot, and checked the guide with Markdown lint. I have left the review thread open for the reviewer.

Posted on behalf of @mnriem by GitHub Copilot (GPT-6 Sol, model ID gpt-6-sol; mode: autonomous; reasoning-effort setting not supplied). AI involvement in this round: documentation correction, source verification, lint check, commit/push, and this summary.

[Copilot]

Copilot review overview

🟢 Approval recommended

The documentation is internally consistent, supported by the referenced repository sources, and introduces no executable behavior.

Review effort: Balanced
Findings: None

Resolved since last review (1)

• Use dotted command names to match historical dogfooding run