feat: K8S KYAML output format support (#2560)

* feat: K8S KYAML output format support

Reference: https://github.com/kubernetes/enhancements/blob/master/keps/sig-cli/5295-kyaml/README.md
Co-authored-by: Codex <codex@openai.com>
Generated-with: OpenAI Codex CLI (partial)
Signed-off-by: Robin H. Johnson <rjohnson@coreweave.com>

* build: gomodcache/gocache should not be committed

Signed-off-by: Robin H. Johnson <rjohnson@coreweave.com>

* chore: fix spelling of behaviour

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

* build: pass GOFLAGS to docker to support buildvcs=false

In trying to develop the KYAML support, various tests gave false
positive results because they made assumptions about Git functionality
Make it possible to avoid that by passing GOFLAGS='-buildvcs=false' to
to Makefile.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

* doc: cover documentScenarios for tests

Signed-off-by: Robin H. Johnson <rjohnson@coreweave.com>

* build: exclude go caches from gosec

Without tuning, gosec scans all of the vendor/gocache/gomodcache, taking
several minutes (3m35 here), whereas the core of the yq takes only 15
seconds to scan.

If we intend to remediate upstream issues in future; add a seperate
target to scan those.

Signed-off-by: Robin H. Johnson <rjohnson@coreweave.com>

---------

Signed-off-by: Robin H. Johnson <rjohnson@coreweave.com>
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Co-authored-by: Codex <codex@openai.com>

pkg/yqlib/doc/usage/headers/kyaml.md

@@ -0,0 +1,9 @@
+# KYaml
+
+Encode and decode to and from KYaml (a restricted subset of YAML that uses flow-style collections).
+
+KYaml is useful when you want YAML data rendered in a compact, JSON-like form while still supporting YAML features like comments.
+
+Notes:
+- Strings are always double-quoted in KYaml output.
+- Anchors and aliases are expanded (KYaml output does not emit them).

pkg/yqlib/doc/usage/kyaml.md

@@ -0,0 +1,253 @@
+# KYaml
+
+Encode and decode to and from KYaml (a restricted subset of YAML that uses flow-style collections).
+
+KYaml is useful when you want YAML data rendered in a compact, JSON-like form while still supporting YAML features like comments.
+
+Notes:
+- Strings are always double-quoted in KYaml output.
+- Anchors and aliases are expanded (KYaml output does not emit them).
+
+## Encode kyaml: plain string scalar
+Strings are always double-quoted in KYaml output.
+
+Given a sample.yml file of:
+```yaml
+cat
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+"cat"
+```
+
+## encode flow mapping and sequence
+Given a sample.yml file of:
+```yaml
+a: b
+c:
+  - d
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+{
+  a: "b",
+  c: [
+    "d",
+  ],
+}
+```
+
+## encode non-string scalars
+Given a sample.yml file of:
+```yaml
+a: 12
+b: true
+c: null
+d: "true"
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+{
+  a: 12,
+  b: true,
+  c: null,
+  d: "true",
+}
+```
+
+## quote non-identifier keys
+Given a sample.yml file of:
+```yaml
+"1a": b
+"has space": c
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+{
+  "1a": "b",
+  "has space": "c",
+}
+```
+
+## escape quoted strings
+Given a sample.yml file of:
+```yaml
+a: "line1\nline2\t\"q\""
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+{
+  a: "line1\nline2\t\"q\"",
+}
+```
+
+## preserve comments when encoding
+Given a sample.yml file of:
+```yaml
+# leading
+a: 1 # a line
+# head b
+b: 2
+c:
+  # head d
+  - d # d line
+  - e
+# trailing
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+# leading
+{
+  a: 1, # a line
+  # head b
+  b: 2,
+  c: [
+    # head d
+    "d", # d line
+    "e",
+  ],
+  # trailing
+}
+```
+
+## Encode kyaml: anchors and aliases
+KYaml output does not support anchors/aliases; they are expanded to concrete values.
+
+Given a sample.yml file of:
+```yaml
+base: &base
+  a: b
+copy: *base
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+{
+  base: {
+    a: "b",
+  },
+  copy: {
+    a: "b",
+  },
+}
+```
+
+## Encode kyaml: yaml to kyaml shows formatting differences
+KYaml uses flow-style collections (braces/brackets) and explicit commas.
+
+Given a sample.yml file of:
+```yaml
+person:
+  name: John
+  pets:
+    - cat
+    - dog
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+{
+  person: {
+    name: "John",
+    pets: [
+      "cat",
+      "dog",
+    ],
+  },
+}
+```
+
+## Encode kyaml: nested lists of objects
+Lists and objects can be nested arbitrarily; KYaml always uses flow-style collections.
+
+Given a sample.yml file of:
+```yaml
+- name: a
+  items:
+    - id: 1
+      tags:
+        - k: x
+          v: y
+        - k: x2
+          v: y2
+    - id: 2
+      tags:
+        - k: z
+          v: w
+
+```
+then
+```bash
+yq -o=kyaml '.' sample.yml
+```
+will output
+```yaml
+[
+  {
+    name: "a",
+    items: [
+      {
+        id: 1,
+        tags: [
+          {
+            k: "x",
+            v: "y",
+          },
+          {
+            k: "x2",
+            v: "y2",
+          },
+        ],
+      },
+      {
+        id: 2,
+        tags: [
+          {
+            k: "z",
+            v: "w",
+          },
+        ],
+      },
+    ],
+  },
+]
+```
+