Feature/2165 interactive template variables

[Paras14]

This PR fixes #2165

Implemented changes:

• Extended VariableSyntax.SQUARE to additionally match $[ask:VARIABLE] and $[secret:VARIABLE] expressions.
• Added IdeContext.askForSecret for masked console input via Console.readPassword.
• During variable resolution, ask expressions for undefined variables prompt the user and persist the entered value to the user's conf/ide.properties so they are not asked again.
• Ask expressions for already defined variables resolve like plain variables without any interaction.
• In batch mode ask expressions are skipped with a warning.
• Updated configurator.adoc and added tests in EnvironmentVariablesTest.

As discussed with @hohwille, the prefix syntax encodes secret vs. plain in the name instead of using function arguments, which aligns it with the $[secret:name] syntax introduced by #2162. A future @function(args) syntax as proposed in #989 can be added as a further alternative in the same regex. Motivated by #412 to preconfigure AI assistant plugins with a backend URL and API key that must not be committed to the settings repository. See also #987.

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Testing instructions

Tested on Windows using PowerShell. Strongly recommended to run an actual PowerShell window, as masking needs System.console(), which is null in IDE consoles and when input is piped, and there the input stays visible
with a warning by design.

1. Build the branch and dump the classpath, from the repository root:

   mvn -pl cli -am install -DskipTests
   mvn -pl cli dependency:build-classpath "-Dmdep.outputFile=C:\temp\cp.txt"
   $CP = (Get-Content C:\temp\cp.txt -Raw).Trim()
   $CLASSES = "C:\projects\IDEasy\workspaces\main\IDEasy\cli\target\classes"
   
   _(make sure you add your path correctly for the cli target classes: "<repo>\cli\target\classes")_
   

2. In a test project create IDEasy\settings\workspace\update\ai-test.properties:

   ai.backend.url=$[ask:MY_URL]
   ai.api.key=$[secret:MY_TOKEN]
   

   Make sure MY_URL and MY_TOKEN are not yet defined in IDEasy\conf\ide.properties.

3. From the project directory, run the local build:

   cd C:\projects\IDEasy
   java -cp "$CLASSES;$CP" com.devonfw.tools.ide.cli.Ideasy update
   

   You are prompted before any downloads: MY_URL with visible input,
   MY_TOKEN with hidden(masked) input. Each prompt names the file requiring it.

4. 4. Check that IDEasy\workspaces\main\ai-test.properties contains the entered values
      with no $[...] left, and that both variables were written to
      conf\ide.properties exactly as typed.

5. Run the same command again. You won't get any input prompts this time, the persisted values are reused.

6. Add MY_OTHER=https://example.com to conf\ide.properties, then add the line
   ai.other=$[ask:MY_OTHER] to IDEasy\settings\workspace\update\ai-test.properties.
   Run again. There is no prompt, and IDEasy\workspaces\main\ai-test.properties
   contains ai.other=https://example.com.

7. Remove MY_URL and MY_TOKEN from IDEasy\conf\ide.properties and run with --batch.
   No input prompts, but one warning per expression, and the $[ask:...] and $[secret:...]
   text is left untouched in the output.

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Checklist for this PR

• When running mvn clean test locally all tests pass and build is successful
• PR title is of the form #«issue-id»: «brief summary»
• PR top-level comment summarizes what has been done and contains link to addressed issue(s)
• PR and issue(s) have suitable labels
• Issue is set to In Progress and assigned to you
• You followed all coding conventions
• You have added the issue implemented by your PR in CHANGELOG.adoc
• You have formulated clear instructions on how to test your contribution under "Testing instructions"

[coveralls]

Coverage Report for CI Build 29803149984

Coverage decreased (-0.04%) to 72.439%

Details

• Coverage decreased (-0.04%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 144 coverage regressions across 6 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

144 previously-covered lines in 6 files lost coverage.

File	Lines Losing Coverage	Coverage
com/devonfw/tools/ide/context/AbstractIdeContext.java	99	70.06%
com/devonfw/tools/ide/environment/AbstractEnvironmentVariables.java	19	81.65%
com/devonfw/tools/ide/context/IdeContext.java	16	78.57%
com/devonfw/tools/ide/context/IdeContextConsole.java	7	0.0%
com/devonfw/tools/ide/variable/VariableSyntax.java	2	85.71%
com/devonfw/tools/ide/version/VersionSegment.java	1	90.03%

---

Coverage Stats

Relevant Lines:	16950
Covered Lines:	12804
Line Coverage:	75.54%
Relevant Branches:	7574
Covered Branches:	4961
Branch Coverage:	65.5%
Branches in Coverage %:	Yes
Coverage Strength:	3.2 hits per line

---

💛 - Coveralls

[QuangAnhLe]

this.context is set in the constructor: ( line 63)

if (context == null) {
this.context = parent.context; // can be null if the root parent is also null
}

If parent is null and context is null → throw IllegalArgumentException. If parent is not null but parent.context is null... the chain might be null. However, in practice, AbstractEnvironmentVariables is always created via AbstractIdeContext.createVariables() → so a context always exists. While this scenario is unlikely, it is best to include a guard. 👍

[QuangAnhLe]

In AbstractIdeContext.askForSecret(), an empty input repeats the loop with no feedback. askForInput() has the same behaviour but at least the user can see what they typed. For masked input the user has no idea if they typed nothing or if the terminal swallowed their input. Consider logging a hint like "Empty input — please enter a value" before the next iteration. :)