template-chart: NOTES.txt and the naked-integer render fix (4.1.0+upxxx)

Two changes to the reference implementation, both of which every chart copied from it inherits.

Render fix (part of #157): multiplyQuantity turned its input into a string with printf "%v". The null-safe fallback helpers pass values through fromYaml, which parses every number as float64, and Go's "%v" switches float64 to exponential notation from about 1e6 upwards - so a bare byte count like 1048576 arrived as "1.048576e+06" and the suffix check aborted the render. A new xxx.formatNumber helper forces plain decimal notation on both the input and the non-integer product; strings like "512Mi" pass through untouched. This is the canonical fix agreed for the issue, taken over verbatim, because multiplyQuantity is the same copy in every chart and a private variant would create drift instead of a solution. The toYaml/fromYaml round-trip is deliberately not touched: it is not the cause.

NOTES.txt (part of #43): the scaffold now carries the reference NOTES.txt - a placeholder-carrying template, not finished prose. It renders the access URL from ingress.domain (no real domain anywhere), names which fields the 1Password item must carry, and prints the chart's traps: the placeholder image, the fact that both a Deployment and a StatefulSet render, and that no checksum/secret-ref means a secret change restarts nothing here. Output is conditional on the values actually set.

appVersion unchanged; minor bump because both changes are additive.

README.md

@@ -115,7 +115,7 @@ If the dependency dashboard reports `Failed to look up github-releases package
 
 ## Creating a new chart
 
-1. Copy `template-chart/` to `<chart-name>/` and replace every `xxx` placeholder: template file names (`xxx.deployment.yaml` → `<app>.deployment.yaml`), `Chart.yaml`, the `values.yaml` keys, the `.Values.xxx.*` references inside the templates, **and both the `xxx.` helper prefixes and the values paths in `values.schema.json`**. Then walk the five points in "Values that must not lie" below — the schema and the null-safe fallbacks are copied with the template, but their content is chart-specific and wrong until you adapt it.
+1. Copy `template-chart/` to `<chart-name>/` and replace every `xxx` placeholder: template file names (`xxx.deployment.yaml` → `<app>.deployment.yaml`), `Chart.yaml`, the `values.yaml` keys, the `.Values.xxx.*` references inside the templates, **and both the `xxx.` helper prefixes and the values paths in `values.schema.json`**. Then walk the five points in "Values that must not lie" below — the schema and the null-safe fallbacks are copied with the template, but their content is chart-specific and wrong until you adapt it. The same goes for `templates/NOTES.txt`: it comes with the template as a worked example and is placeholder text until you replace it with what an operator of *your* app needs after the install (see "Everything else" below); its leading `{{/* … */}}` block explains the bar and is meant to be deleted.
 2. Add `.github/workflows/publish-<chart-name>.yml` (copy an existing one, e.g. `publish-outline.yml`).
 3. Add the chart name to the choice list in `.github/workflows/change-app-version.yml`.
 4. Add a `customManagers` block for the chart's main image in `renovate.json5` (copy a neighbouring one, swap `managerFilePatterns` and `depNameTemplate`) — without it the chart's app version is never updated. Check the image's tag list first: if it carries a flavour, date or prerelease suffix, add a `versioningTemplate` with a comment saying why.
@@ -256,6 +256,6 @@ Reference implementation: `template-chart/values.schema.json` and `template-char
 
 - `icon:` is mandatory in every `Chart.yaml`. **Documented exception — freesailarr, the only chart without one**: the rule everywhere else is "the icon is this chart's one upstream's logo", and a chart bundling nine independently versioned projects has no such upstream — picking one of the nine would imply a "main app" the stack deliberately does not have. That is the whole criterion, and it applies to no other chart in the repo: a single-upstream chart without an icon is a missing icon, not an exception. The omission costs an INFO line in `helm lint --strict` (`icon is recommended`), which still exits 0.
 - `helm lint --strict` must pass without findings.
-- `NOTES.txt` for every chart is planned (#43); eight charts ship one so far (`apache-tika`, `cyberchef`, `freesailarr`, `gotenberg`, `homeassistant`, `patchmon`, `rss-bridge`, `searxng`).
+- `NOTES.txt` for every chart is planned (#43); nine charts ship one so far (`apache-tika`, `bentopdf`, `cyberchef`, `freesailarr`, `gotenberg`, `homeassistant`, `patchmon`, `rss-bridge`, `searxng`). Reference implementation: `template-chart/templates/NOTES.txt`, which is a placeholder-carrying template rather than finished prose — a new chart adapts it instead of starting from an empty file. The bar it sets: print what an operator would otherwise have to look up in the templates (the rendered access URL, **which fields the 1Password item must carry**, the options actually active in this release, and the chart's known traps), conditional on the values really set. A `NOTES.txt` that only repeats the values is skimmed once and never read again. **No real domain anywhere** — the URL renders from `ingress.domain`, and where an example is unavoidable it is `example.com`. Adding one renders no Kubernetes object, so it is purely additive: a minor bump.
 - CI: every installable chart has fixtures under `ci/<chart>/` (`test-values.yaml`, optionally `fixtures.yaml`/`fixtures.env.yaml`/`settings.env`) or a justified entry in `ci/excluded-charts.txt` — the install-test fails if both are missing.
 - Charts have no dependencies (`charts/` directories are empty).