chore: wire .github/instructions to AGENTS chain; add secret-block and constraints-warning rules

[bkenez]

Which problem does the PR fix?

Closes #6460

Agent guides in .github/instructions/*.instructions.md carry Copilot applyTo: globs that Claude Code does not auto-apply. The CLAUDE.md → AGENTS.md chain never pointed there, leaving agents with no routed path to the conventions. PR #6426 demonstrated this: the @param conjunction rule was already documented in values-yaml.instructions.md yet violated PR-wide — because no agent path reached that file.

Two additional conventions were missing entirely: the canonical secret: block shape (ADR-0068 standardization) and the rule that render-time warnings belong in camunda.constraints.warnings, not hand-written in NOTES.txt.

What's in this PR?

• AGENTS.md — "Additional Agent Context" now lists .github/instructions/*.instructions.md as authoritative path-scoped chart-coding conventions with an explicit read-before-editing instruction.
• .github/AGENTS.md — one-line pointer to the instructions library added under ## Conventions.
• .github/instructions/values-yaml.instructions.md — §6 (formerly "Optional Secret Pattern") rewritten as "Secret Block Pattern": canonical inlineSecret/existingSecret/existingSecretKey key order, multi-secret reference (documentStore), the auxiliary-keys-go-beside-not-inside rule, and "don't invent new formats" citing ADR-0068. Common Mistake Standalone Gateway pod 9600 endpoint returns 503 Service Unavailable #11 added.
• .github/instructions/helm-templates.instructions.md — NEVER/ALWAYS rules for constraints/warnings, Core Pattern Add elastic exporter as optional dependency #10 (hard-fail vs soft-warning shapes in constraints.tpl), Common Mistake Add extra container and init container values #9. constraints.tpl added to Resources.

Checklist

Before opening the PR:

• In the repo's root dir, run make go.update-golden-only.
• There is no other open pull request for the same update/change.
• Tests for charts are added (if needed).
• In-repo documentation are updated (if needed).

After opening the PR:

• Did you sign our CLA (Contributor License Agreement)? It will show once you open the PR.
• Did all checks/tests pass in the PR?

[Copilot]

Pull request overview

This PR updates the agent guidance “entry points” so that Claude-facing agent chains explicitly route contributors to the path-scoped convention library under .github/instructions/, and it adds/clarifies conventions for the canonical secret: block shape and for where render-time warnings/constraints must be authored.

Changes:

• Link .github/instructions/*.instructions.md into the CLAUDE.md → AGENTS.md → .github/AGENTS.md guidance chain so conventions are discoverable outside VS Code’s applyTo: routing.
• Expand values-yaml.instructions.md with a canonical 3-key secret: block pattern and “aux keys beside, not inside” guidance (ADR-0068 reference).
• Expand helm-templates.instructions.md with constraints vs warnings guidance (constraints.tpl vs NOTES.txt) plus examples and resources.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
AGENTS.md	Adds an explicit pointer to the .github/instructions/ library in the “Additional Agent Context” chain.
.github/AGENTS.md	Adds a conventions pointer to the .github/instructions/ library, clarifying Claude Code routing limitations.
.github/instructions/values-yaml.instructions.md	Documents the canonical secret: block shape, ordering, and multi-secret/aux-key placement rules, referencing ADR-0068.
.github/instructions/helm-templates.instructions.md	Documents constraints vs warnings authoring patterns and prohibits hand-written render-time warnings in NOTES.txt.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.